A year after escaping from Moscow in a Mig-30 jet, a Soviet defector hires Magnum to help his girlfriend defect from an Olympic track team visiting Hawaii. She is under close watch of undercover K.G.B. agents, and Magnum, T.C., and Rick, with assistance from Higgins, must carry out their plan with Military precision to free her...

Thomas awakes from a bad car accident in which he drove the Ferrari over a cliff on his way home from dinner with his clients, for whom he was searching for a missing young woman; the accident leaves him with amnesia, and as he struggles to remember the events that lead up to the crash, he becomes the prime suspect when the girl he was looking for is found murdered, and one of his baseball caps is found at the scene of the crime.

It is Thomas' birthday, and he is hired by expert card player Jeanie Lowry, nick-named 'Texas Lightning' to act as her body-guard at a high stakes poker game on-board a luxurious yacht the coming night. Thomas is at first reluctant to take a body-guard job, but the large cash fee offered soon persuades him. But during the card game, Jeanie slips away and breaks into shady yacht owner Thompsons' safe. The break in is discovered and Thompson is ready to kill both Thomas and her, but they manage to escape and wind up stranded on a small island. Magnum and Jeanie are presumed dead, but Higgins, T.C. and Rick refuse to believe it and set out to search for them – but Thompson looks set to find them first. Worse still, all along, Jeanie is far from being what she claims to be...

Thomas is certain that Higgins is pulling some kind of prank when he supposedly meets Higgins' illegitimate half-brother Elmo Ziller, a guitar-plucking, 10-gallon-hat wearing Texan rodeo owner. Elmo was rumoured to have been killed in Texas recently, but with him seemingly still alive, his daughter hires Magnum to protect what is supposedly Elmo from the killers while his rodeo show is in Honolulu. Even though he is persuaded to take the case, Thomas is still certain that Higgins and Elmo are one and the same...

William Troubshaw, an old adversary of Higgins who had made his life misery at school, married the girl he once loved, and eternally the bane of Higgins' life, has recently moved to the islands with his family, and they two old rivals are scheduled to compete against each other in an upcoming fencing tournament. But during the duel, Troubshaw is suddenly killed in seemingly a freak accident, when Higgins' foil sets off his hit indicator, causing him to be electrocuted. Higgins becomes suspect for murder when his fingerprints are found on the rewired scoring box. Magnum is certain that Higgins couldn't have been responsible for the killing, and sets about finding the real culprit behind the death, but the evidence and motives are stacked up against Higgins, and for some reason, he is refusing to call upon Robin Master's top lawyers and is just going along with the allegations...

When a highly eccentric, practical joke-loving and not very well liked millionaire Wilson MacLeish is killed when his new bi-plane explodes, Thomas, who had been working on a case for him, is summonsed to the reading of the will. Read out via a video-tape, the deceased millionaire leaves his ex-manservants some money, but leaves his relatives practically nothing, instead leaving his estate and wealth – fifty million dollars - to Thomas! MacLeish's relations are put out and angered by this, and Thomas takes up his new residence on the estate. On a second video-tape, MacLeish informs Thomas that before his death he had suspected that one of his relations is trying to kill him for his inheritance, and wants Thomas find out who. But it begins to seem that whoever may have been responsible for the millionaire's death is now trying to bump Magnum off too...

Robin Master's mentor, Elizabeth Barrett, arrives at the estate with her macaw Merlin to research a book on ornithology. The former teacher hits it off famously with Thomas, but becomes so much of a thorn in Higgins's side that he bribes Thomas to help in bringing her visit to an expeditious end by finding Dr. Albert Tessa, the reclusive bird expert she's come to the island to interview. Thomas soon discovers that Elizabeth isn't Robin's mentor, but a K.G.B. agent on a mission to assassinate Tessa, a refugee freedom fighter from the 1956 Hungarian revolt. Meanwhile, Thomas has troubles collecting his fee from a man whose beautiful employee is tough enough to shoot out the Porsche's windscreen to keep Thomas at a distance from her boss.

As part of the research for an upcoming Robin Masters novel, Higgins contacts a witness in the 1942 murder of a prison camp inmate by a civilian guard, and soon after is badly injured in an accident when the Ferrari's brakes fail. When the mechanic confirms that someone has tampered with the car, Thomas sets out to find who wants to stop Higgins's research, and uncovers blackmail and shady politics at the center of the case.

Rod Crysler, Thomas's Navy buddy, is on parole and working as an encyclopedia salesman after serving time in California on a marijuana possession charge. The corrupt narcotics officer who arrested Rod follows him to Hawaii and threatens to send him back to prison on trumped up charges unless Rod serves a drug courier for him. Thomas offers to help his buddy out by delivering a box of encyclopedias Rod has sold, but comes in for a rude awakening when it turns out the package was filled with dope, not books, and that Rod has shortchanged one of the biggest dealers on the island. Finding it hard to believe that his friend is a dope dealer, Thomas seeks the help of Rod's parole officer in locating him and setting up a sting to ensnare the corrupt cop and the drug dealer, thereby clearing Rod's name.

It is Christmas Eve, and T.C. is flying Rick to judge a beauty pageant, Thomas to play Santa Claus at a charity event, and Higgins to deliver a payroll to some of Robin Master's workers, before he goes home to spend Christmas with his family in New Orleans. But the helicopter suddenly develops problems and they are forced to make an emergency landing on nearby deserted Frenchman's Island. The remote isle is used by the Navy for shelling manoeuvres – and as the foursome try to find a way to safely make it off of the island, hopefully in time for Christmas, a Naval Captain, unaware of their presence, is hell-bent on upping his ship's target practice scores, and a shelling on the island is imminent...

Thomas is forced to forgo his much-anticipated trip to the Army-Navy game and a reunion with his 1967 championship teammates when Rick, T.C., and Higgins guilt him into remaining in Hawaii and helping Carol save her career by nabbing one of the largest drug distributors in the islands.

First in a two-part story. Tyler McKinney, an old commando acquaintance, asks Thomas, Rick and T.C. to help him rescue a buddy who is held prisoner after being captured in Chong Ker, Cambodia. The three have no reason to like or trust McKinney after he involved them in a dubious mission in Vietnam, but individually they all eventually agree to help him on the mission. They head off to Cambodia, with the unexpected accompaniment of Higgins, but the mission has dangerous consequences in store for Rick...

Conclusion of this two-part story. Magnum, Tyler and Higgins are held prisoner by the Vietnamese Major that has a reign of terror over Chong Ker. As Rick lays recovering from his wounds, T.C. works with a local he's befriended trying to repair an old helicopter for their escape, but it becomes apparent that Tyler has been deceitful about the true nature of the mission...

Magnum is called back to Naval service by Admiral Hawkes, who has reason to suspect that there is a security leak at his Naval base that is leaking coded information, but can't ask any of his personnel to investigate for any one of them could be the ""mole"" behind the breach. He needs Magnum to root out the mole and plug the leak within three days, when he is due to receive some important submarine manuals written in code, which could be potentially very dangerous if they got into the wrong hands. Thomas' prime suspect is the fiancée of the Admiral's son, but when some stolen classified information is planted in his car, he himself accused of espionage...