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.
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.
The 9-1-1 Call Center goes up in flames: Bobby risks his life to save May and Claudette, Buck and Eddie work together to help an injured electrician and Chimney and his brother team up as firefighters for the first time.