An emergency alert of an impending missile attack sends Los Angeles into chaos and uncertainty, while the officers each try to keep the peace and deal with their own disasters.
Nolan is given some life-changing news and invites Grace over for a home-cooked meal in his newly remodeled kitchen; each unit is tasked with following up on dormant cases in hopes of uncovering new leads.
Officers Nolan, Chen and West are squeezed harder than ever before as their training officers evaluate whether they are truly ready for the job; one of the rookie classmates is involved in a shooting.
Nearing the end of his training, John Nolan now faces his biggest challenge as a police officer when he must come to terms with the choices he has made in pursuit of the truth.
The team responds to the report of a severed hand washing up on the beach and are on the hunt to find its owner; Tim attempts to prove he isn't a control freak to Lucy and invites her on a double date with him and Ashley.
