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.
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.
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.
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.
Sgt. Grey supports Officer Nolan's desire to become a training officer and offers to ride with him for the day to get him ready; Tim and Lucy decide on their plans for Mother's Day and a romantic vacation.
