Nolan teams up with new night detective Nick Armstrong for a murder investigation case that results in an unexpected reunion with a former love interest. Officer Bradford reluctantly accepts help from Officer Chen as he prepares for his sergeant exam, and Officer West pursues an unconventional move after finding himself in need of a new home.

As part of their second phase of training, the rookies are asked to develop their first confidential informants. Officer Nolan soon discovers that no two informants are the same and struggles with his newest task. Meanwhile, Officer Chen’s mother complicates her home life when she comes to stay with her.

Officer Nolan’s trust is tested when he tries to help the previous owner of his home reconnect with his family. Meanwhile, Officer Harper has finally earned an overnight visit with her daughter that is put into jeopardy when her past undercover life resurfaces again.

Officer Nolan and team are charged with escorting a notorious female serial killer to the graves of her previously unrecovered victims. However, when they arrive, they unearth even more than they expected. Meanwhile, Officer Chen meets a seemingly perfect man who sparks her interest, and Officer Lopez worries about Wesley as his PTSD continues to increase.

Officer Nolan and the entire team are in a desperate search to rescue Officer Chen after her abduction and must attempt to get Rosalind to help them in their search. Meanwhile, after Officer Lopez discovers Wesley unconscious from a dangerous cocktail of alcohol and pills, she is forced to keep him close by.

Officers Nolan and Harper investigate a murder which may have national security implications, while Officer Bradford must confront his past when he crosses paths with a homeless veteran.

Officer Nolan is having a particularly bad day after learning his identity has been stolen and could jeopardize his position as an officer. Meanwhile, Sgt. Grey must confront his past and testify at the parole hearing of the man who shot Grey and murdered his partner.

Officers Nolan and Harper are tasked with escorting four juvenile offenders to a Scared Straight program at a correctional facility that quickly becomes a riotous situation. Meanwhile, Nolan is uncertain about his relationship with Grace after she fails to introduce him to her ex-husband.

Their rookie year is coming to an end and officers Nolan, Chen and West are about to be squeezed harder than ever before as their training officers evaluate whether they are truly ready for the job. Meanwhile, after one of their rookie classmates is involved in a shooting, the team uncovers some unsettling evidence .

Nolan's discovery goes much deeper than he expected and could put his life and career in jeopardy.

Nearing the end of his training, Nolan now faces his biggest challenge as a police officer yet when he must come to terms with the choices he has made in pursuit of the truth.