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.
The rookies are really put to the test when their training officers accompany them out of uniform for Plain Clothes Day, which forces them to make all the decisions while on patrol. Meanwhile, Officer Nolan tries to prove he has been progressing faster than the other rookies to justify his desire of becoming a detective within five years.
When one of their colleagues is arrested by Internal Affairs for lying on the witness stand, it leads to the release of three felons whose cases he worked on and the team being asked to check in on them now that they are free. Meanwhile, Officer Nolan finds out he is being sued by a man who claims he used excessive force which led to an injury.
Nolan, the rookies and their training officers get involved in a competition that pits them against each other, while Officer Lucy Chen notices Officer Tim Bradford is obsessed with winning at all costs.
As the rookies prepare for a big exam to see who moves on to the next stage of training, Officer Nolan and Officer Bishop are called to the scene of a murder and learn that the victim may be tied to a potential terrorist attack on the city of Los Angeles.
Sergeant Grey informs Officer Nolan and Officer Bishop that they are going to have a movie director as a ride-along during their patrol after a fun afternoon granting the wish of a Make-A-Wish kid as honorary police officer Kaydence Patton. Meanwhile, Officer Bradford is tested once again after he learns that his wife, Isabel, has been arrested for drug possession.
The rookies become the prime suspects after it is discovered a large sum of money used in a drug bust has gone missing.
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.
A massive earthquake rocks the city and throws everyone’s patrols and its citizens into chaos. Meanwhile, agent Russo (Sarah Shahi) recommends Officer Nolan for a protective detail of Brad Hayes (Joel McHale), a man whose dealings have put a target on his head.
Nolan and the team must help capture a cop and his former mentor from the academy after he becomes a fugitive following...