Athena, Maddie, Bobby, and the 118 race to save lives after a massive tsunami hits the Santa Monica Pier; Buck fears the worst when Christopher goes missing.
After a victim of the apartment fire that changed Bobby's life resurfaces, he searches to make amends. Driven by his need to right past wrongs, Bobby delves deep into memories of his childhood, unearthing moments from his fractured past.
When a murder weapon from a case close to Athena in the early '90s resurfaces, flashbacks to 1989 show how Athena joined the LAPD and became the police officer she is today.
In the aftermath of the shooting, Athena and the 118 are on high alert when a sniper is targeting members of the LAFD. Meanwhile, Maddie makes a life decision.