Leo follows Marcus to his secret lair (an abandoned train station) to gather evidence that proves he's bionic but ends up captured by Marcus and told that there bionics are just some dumb tricks. Meanwhile, the Lab Rats scramble to bring Tasha back before Davenport finds out that they accidentally teleported her to parts unknown.

The truth behind Marcus and his father.

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When Mr. Davenport invents a new freeze ray gadget, he sends the Lab Rats on a mission to Antartica to collect ice-type fuel for his invention. But when a 'category 5' storm hits Antartica, he calls the mission off. Ignoring Davenport's orders, Chase goes anyways, alone and gets trapped in an avalanche after it collapsed on him. When he tries to find a way out, he runs into Douglas along the way. Meanwhile, Leo tries to impress Janelle, but accidentally freezed her using Davenport's freeze ray gadget.

The Lab Rats are forced to expose their bionic secret in order to save Principal Perry.

Leo and Donald escape the elevator. Principal Perry lets them stay at the school temporarily in order to get her money from Donald quicker. The Lab Rats stow away on a cargo ship to hide from the FBI and must choose to either keep quiet or help stop a submarine that will crash into the ship and risk being caught. The Lab Rats decide to stop the submarine, with Chase activating his GPS, revealing the Lab Rats' location. Douglas ends up capturing them, disguised as Donald. Douglas reveals that his new bionic partner is a billionaire named Victor Krane, who wants to destroy the Lab Rats permanently. When Donald calls the Lab Rats and tells them that Principal Perry kept their secret, they return home, only for them to get crazy as a result of the Triton App and attack the family, Leo manages to disable Chase's Triton App when he talks to him and Chase manages to disable Adam and Bree's apps. The Lab Rats and the family later see the demolition that happened to the lab and are upset.

Leo and Donald escape the elevator. Principal Perry lets them stay at the school temporarily in order to get her money from Donald quicker. The Lab Rats stow away on a cargo ship to hide from the FBI and must choose to either keep quiet or help stop a submarine that will crash into the ship and risk being caught. The Lab Rats decide to stop the submarine, with Chase activating his GPS, revealing the Lab Rats' location. Douglas ends up capturing them, disguised as Donald. Douglas reveals that his new bionic partner is a billionaire named Victor Krane, who wants to destroy the Lab Rats permanently. When Donald calls the Lab Rats and tells them that Principal Perry kept their secret, they return home, only for them to get crazy as a result of the Triton App and attack the family, Leo manages to disable Chase's Triton App when he talks to him and Chase manages to disable Adam and Bree's apps. The Lab Rats and the family later see the demolition that happened to the lab and are upset.

Donald shows a new motorcycle to the Lab Rats when they get a video message from Douglas that Krane has lost it and implanted himself with more bionic abilities, abilities even he doesn't know about. The Lab Rats instead believe this to be a trap, leading Donald to activate a new security system that only he can bypass. While Leo is at Mission Creek High School, Douglas arrives and tries to appeal to Leo by reminding him that he knew about Douglas and Marcus before the rest of them. Douglas then shows Leo video footage of Krane implanting himself with bionics and asks him to call his brother to prove his honesty. Back at the lab, a transmission comes in and shows Leo and Tasha captured. While Donald thinks it's Douglas, Krane reveals himself on-screen as the captor and demands that the Lab Rats arrive in 10 minutes. While the Lab Rats want to rescue them, Donald heads out alone with an extremely powerful thermal blaster. Donald arrives at Krane's lair, only for Krane to siphon the power from the blaster, rendering it useless and quickly beating Donald with super strength and molecularkinesis. During the battle, Leo and Tasha are trapped in an exothermic energy field to fry them. Afterward, Krane geo-leaps to the lab, allowing Donald to use the thermal blaster to suck in the heat to set Leo and Tasha free. As Chase works to deactivate the security system, Krane arrives and easily beats the Lab Rats with his more advanced bionics. Before Krane can finish them off, Douglas arrives and blasts Krane with a laser blaster. Although he saves the Lab Rats, Krane quickly recovers and knocks him down with another force wave. As he once again prepares to attack, Chase repels his blast back at him with a force-field, defeating him for good. Douglas plans to capture the unconscious Krane, but Donald arrives and blames the entire mess on him. Unfortunately, Krane geo-leaps out of the house and Donald demands that Douglas leaves.

As Donald attempts to repair Bree's damaged chip, the replacement chip keeps malfunctioning, much to Donald's frustration. Although Leo believes Douglas can help since he was the original creator, Donald refuses to even see his brother again. Realizing Donald won't change his mind, Leo finds Douglas, anyway, who reluctantly agrees to help. While Donald is away, Douglas creates a new chip as close to the original as possible, and though it seems to work, it also malfunctions by causing Bree to run uncontrollably. Donald finds Leo with Douglas at the lab, but helps out and all three manage to keep Bree still; however, they still can't find a solution. After several minutes, they finally find the error and collaborate for the first time in years, fixing Bree's chip and saving her life. Meanwhile, Adam and Chase try to find a way to replace Bree's speed. While Chase manages to power up Donald's motorcycle to go 350-400 MPH, it runs out of gas almost instantly. After Bree's chip is fixed, Donald still kicks out his brother. While watching Bree apologize for her mistake, Donald realizes everyone deserves a second chance. The next morning, Donald offers his brother a chance to move in with them temporarily, and he accepts.

When the Lab Rats are on a mission, it is revealed that a girl was secretly recording them behind a bush. The next day, the Lab Rats go to school and everyone is looking at a viral video called The World's First Bionic Humans. They go back home to tell Donald, but he says he already knows. Meanwhile, Chase is confused that he didn't notice the girl who filmed them behind the bush, even though he thermal scanned the whole place. He then looks at a chip log and finds out that the girl was in the exact spot he scanned. Chase then goes to tell Donald, but a swarm of government agents surrounds them. Leo and Douglas are still in the lab, but they use a trap door to escape and go to school to stay safe. It is then revealed that the mission the Lab Rats were on was a setup. Krane then shows up with the girl who filmed the Lab Rats, whose name is revealed to be S-1. It is also revealed that she is bionic. Krane electrocutes Principal Perry and Douglas while S-1 crushes Leo's arm. Later, Douglas and Principal Perry help Leo to get his arm fixed and take him to the hospital. Tasha later shows up, only to realize that Leo is gone. While the Lab Rats are saying their goodbyes, Special Agent Graham tells them it's time to leave, but Adam refuses. Agent Graham orders his agents to take them down, but Adam uses his wave blast ability to knock them down. When they run to the hospital, Principal Perry tells them Krane is responsible for exposing their bionics. Meanwhile, Leo is in Douglas and Krane's old warehouse and Douglas tells him to take his bandage off and pretend to throw a ball. He then realizes that Douglas upgraded his right arm with bionics. Krane then shows up and knocks down Leo and Douglas. The Lab Rats then show up with Donald, as Krane uses a powerful bionic ability that knocks out Leo, Donald, and the Lab Rats. Krane then paralyzes Donald with his choking ability. Bree battles S-1 while Adam and Chase battle Krane, but he easily takes them down with his newly upgraded Triton App that he uses on S-1. Leo then uses his bionic arm to take down Krane. As Agent Graham arrives, Douglas reveals that Krane and S-1 are the bionic villains. Agent Graham is then saved by Bree as Krane tries to attack him and he takes Krane and S-1 into custody and locks them in a prison with a bionic signal interrupter, preventing them from using their bionics to get out. Later, the Lab Rats are at a press conference and reveal that they are bionic superhumans. While watching it, Principal Perry makes new friends with the Lab Rats. In the end, Agent Graham tells Donald he's now in charge of the Lab Rats. It is also revealed that Krane has an army of bionic soldiers, which he will use to destroy the Lab Rats.

When the Lab Rats are on a mission, it is revealed that a girl was secretly recording them behind a bush. The next day, the Lab Rats go to school and everyone is looking at a viral video called The World's First Bionic Humans. They go back home to tell Donald, but he says he already knows. Meanwhile, Chase is confused that he didn't notice the girl who filmed them behind the bush, even though he thermal scanned the whole place. He then looks at a chip log and finds out that the girl was in the exact spot he scanned. Chase then goes to tell Donald, but a swarm of government agents surrounds them. Leo and Douglas are still in the lab, but they use a trap door to escape and go to school to stay safe. It is then revealed that the mission the Lab Rats were on was a setup. Krane then shows up with the girl who filmed the Lab Rats, whose name is revealed to be S-1. It is also revealed that she is bionic. Krane electrocutes Principal Perry and Douglas while S-1 crushes Leo's arm. Later, Douglas and Principal Perry help Leo to get his arm fixed and take him to the hospital. Tasha later shows up, only to realize that Leo is gone. While the Lab Rats are saying their goodbyes, Special Agent Graham tells them it's time to leave, but Adam refuses. Agent Graham orders his agents to take them down, but Adam uses his wave blast ability to knock them down. When they run to the hospital, Principal Perry tells them Krane is responsible for exposing their bionics. Meanwhile, Leo is in Douglas and Krane's old warehouse and Douglas tells him to take his bandage off and pretend to throw a ball. He then realizes that Douglas upgraded his right arm with bionics. Krane then shows up and knocks down Leo and Douglas. The Lab Rats then show up with Donald, as Krane uses a powerful bionic ability that knocks out Leo, Donald, and the Lab Rats. Krane then paralyzes Donald with his choking ability. Bree battles S-1 while Adam and Chase battle Krane, but he easily takes them down with his newly upgraded Triton App that he uses on S-1. Leo then uses his bionic arm to take down Krane. As Agent Graham arrives, Douglas reveals that Krane and S-1 are the bionic villains. Agent Graham is then saved by Bree as Krane tries to attack him and he takes Krane and S-1 into custody and locks them in a prison with a bionic signal interrupter, preventing them from using their bionics to get out. Later, the Lab Rats are at a press conference and reveal that they are bionic superhumans. While watching it, Principal Perry makes new friends with the Lab Rats. In the end, Agent Graham tells Donald he's now in charge of the Lab Rats. It is also revealed that Krane has an army of bionic soldiers, which he will use to destroy the Lab Rats.

Leo tries to show off his bionic arm to Janelle. Meanwhile, Agent Graham promotes the Lab Rats as bionic celebrities, but when they realize they missed a mission because of him, they decide to get Donald back as their leader by pretending to have glitches in their bionics to humiliate Graham in front of the President of the United States when he comes to visit them. In the end, Donald is back as their leader after Agent Graham is fired by the president, arrested by the Secret Service, and sent to prison.

Chase feels that it is unfair to be picked on by Adam every time and tells Donald. Douglas overhears and unlocks a new ability for Chase, upsetting the balance in the house. Douglas tries to fix things by giving Adam a new ability as well, but Adam and Chase end up fighting with one another. Meanwhile, Bree tells Leo about a contest at Tech Town as they are about to hit their one-millionth customer and Leo competes to ride on the first anti-gravity roller coaster and meet the owner of Tech Town. Principal Perry tries to compete to crush Leo's dream. In the end, Chase and Adam have a death battle, but eventually forgive each other and find out that Douglas gave Bree the ability to go invisible, scaring everyone in the lab.

Bree wants to get revenge on Adam for embarrassing her in front of her boyfriend, Jake. Working with Chase, she puts on a cyber cloak that makes her look and sound exactly like Principal Perry and embarrasses Adam in front of the whole school. However, when she shows Adam the cyber cloak right before the dance that night, it glitches and won't come off. Bree then makes Chase wear a cyber cloak of herself and go to the dance with Jake. While that's going on, Leo and Douglas snoop in Donald's briefcase and compete for what they think is to be his new vice-president, only to find out it was for the Davenport Industries softball team. Donald then finds out that he had two cyber cloaks missing and deactivates them. This embarrasses Chase and gets Bree into trouble with Jake. She then thinks she's patched things up with Jake, but it's really Principal Perry wearing a cyber cloak.

The Lab Rats plan to gain good publicity by having cameramen film them during a mission, but it turns into a disaster when they fight for screen time. After the mission, the president orders the team to stay away from the public in order to let him settle things down. However, it goes wrong when Leo and Principal Perry are holding back angry protesters who want the Lab Rats gone, and Leo accidentally uses his bionic arm. As the protesters become even more enraged, they try to storm the house; Adam panics and uses his bionic super breath to blow everyone off the premises. However, Chase criticizes Adam's actions and the Lab Rats start fighting. They eventually decide to break the team. Three weeks later, the Lab Rats refuse to talk to each other, but they are forced into action when Krane plans to use his Triton App on everyone in the world. A large battle ensues, pitting Leo, Donald, Douglas, and the Lab Rats against Krane and his bionic army. Most of the soldiers attack Adam and Bree, who manage to take them out. Chase has a one-on-one battle with S-3 and Leo has one-on-one battle against S-1. Donald and Douglas attack the soldiers surrounding the satellite, but Krane keeps them from getting too close. Eventually, the Lab Rats and the rest of the team manage to hold back many of the soldiers, but they are running out of time to stop Krane. Douglas then reveals that the Lab Rats can fuse their abilities to stop Krane. They succeed, blasting Krane into the sky and breaking his control over the soldiers. However, their victory is cut short when they find out that Donald is in serious condition after the battle. Later they find out that after the surgery, Donald is still in a very delicate condition. Leo is made an official member of the Lab Rats and gets an upgrade to his bionic arm.

When suspicious events happen overnight on the bionic island, everyone is convinced a new threat has emerged. However, this threat is revealed to be Leo, when his bionics glitch because Douglas never gave Leo a capsule.

Adam brings a dog back to the island and Douglas reveals that it's his old dog, Otis, who Douglas made bionic in order to save his life when Otis was injured. Chase turns out to be allergic to dogs as he starts sneezing, so Douglas says that Otis has to leave, but he and Adam actually hide the dog. Meanwhile, Leo gets a new smartphone application assistant named Shelly, with whom he has fallen in love.

The Lab Rats are on a mission to save people from a wildfire; when the people start to chant Adam, Bree, and Chase's names, Leo gets jealous and wants to become known. Douglas gets put in charge to develop a new technology for the academy, but can only come up with things that can hurt the students.

Chase and Douglas reanimate a prehistoric sea spider. It escapes and bites Adam, which poisons him. It then grows and becomes 50 feet long due to growth hormones that had been given to it by Douglas. Everyone tries to stop the spider so they can create a cure for Adam.

Douglas finds out that there is a student named Kate with the Commando App. Chase tries to activate her Commando App, named Spikette by Douglas, so he can research her. When he starts fighting with Adam, she activates her Commando App and thinks Chase is her baby. While she destroys the bionic academy, Bree forces Chase to activate his Commando App by embarrassing him so he and Kate can battle. Unfortunately, he teams up with her. Douglas gives Bree a Commando App and she and Kate begin battling each other. Bree wins and Douglas extracts Kate's chip. Chase apologizes to Kate and finds out that Douglas replaced her Commando App with sonic screaming.

Douglas tells the group that his old college ex-girlfriend, a film director named Giselle, will be making a film titled Bionic Action Hero based on all of them and starring an up-and-coming actor named Troy West. Giselle and Troy visit the island to learn about the bionic team.

Douglas tells the group that his old college ex-girlfriend, a film director named Giselle, will be making a film titled Bionic Action Hero based on all of them and starring an up-and-coming actor named Troy West. Giselle and Troy visit the island to learn about the bionic team.

Adam, Bree, and Chase are looking for Leo because he is late for training and find out he is in Mission Creek because Janelle threatened to break up with him. S-1 shows up unexpectedly and shocks everyone. She came to the island because, like everyone else, her memory is blank, but has continuing flashbacks of Krane.

Douglas creates a device that makes any bionic human as smart as Chase. After Douglas tests it on Bob, Bob starts spending time with Chase. This leaves Adam in envy. Meanwhile, Perry made the island officially her own, which makes Bree and Leo angry at her.

Leo just finishes his movie marathon while everyone else is frustrated because they have nothing to do on Halloween. Bob intentionally stays behind while the other students are away with Davenport to a museum. Perry says she's going to another island across from theirs, but Douglas says no because it's deserted and has been uninhabited for years. When Douglas leaves, the group decides to go anyway.

Donald tells the group that the president has decided to host an award ceremony because they have completed their one-thousandth mission and Leo wants his recognition, but it's only for the original members. Disappointed, Leo forms his own team with S-1, who calls herself Taylor now, and Logan.

Everyone is shocked when Douglas introduces a fourth bionic sibling named Daniel who’s been living a normal life with an adopted family. Daniel later comes to the academy to meet his father, uncle, and cousins. After Daniel's bionics are accidentally activated by the Lab Rats, Donald and Douglas find out what happened they have to come clean to Daniel about his power-replicating abilities. Daniel also finds out that his cousins are actually his biologic siblings. Filled with anger, Daniel goes out for air on the beach, where Leo and him have a conversation about Douglas. Not too long after, Daniel, using Leo's abilities, accidentally causes a leak in the hydro-loop's fuel tank. After Adam and Daniel combined their powers to stop it, Douglas apologizes to Daniel for lying and Daniel decides to give Douglas a second chance.

Donald and Douglas reveal that they have built an upgrade for all the students bionics, except for Leo's. But the upgrade doesn't work on Adam, Bree, and Chase because their systems are older. Adam, Bree, and Chase are therefore left at their level, while all the students are much more powerful. Meanwhile, Daniel is brought to the Academy because he had been using his bionics in the outside world. Douglas decides to enroll Daniel at the Academy, and he makes Leo his mentor. Leo steadily tries to teach Daniel, but Daniel proves to be unteachable, so Leo gives him the upgrade as well. The students steadily start to vanish, including Daniel. Giselle Vickers, Douglas' old girlfriend, is revealed to have captured them. Daniel sends a video message to the Island, requesting help.

Giselle reveals she dug up Marcus from Douglas' old lair and rebuilt him, piece-by-piece. Marcus wants revenge on Douglas for leaving him to die. Everyone rushes Giselle and Marcus, but Marcus knocks everyone unconscious. Donald and Douglas are tied together in chairs, while Adam, Bree, Chase, and Leo are put in the chamber with the students, while Daniel is pulled out.