When a heat wave hits Seattle, Station 19 becomes a cooling center and chaos ensues with locals who aren't used to the extreme temperatures. Andy deals with regret and finds a friend in Theo. Joey comes face-to-face with his past during a ride-along with Ben and Jack.

When Theo and Vic hit a relationship milestone, Vic is forced to reckon with her feelings about commitment. Andy takes refuge at Dean's home and helps care for Pruitt, while Dean considers a new potential career opportunity. Meanwhile, an explosion rips apart a neighborhood and changes the lives of our firefighters forever.