Relationships are challenged at Station 19 following Sullivan's actions at Maya and Carina's wedding, putting his marriage with Andy to the test. Dean comes to terms with his feelings for Vic while Travis rekindles an old flame.
When a heat wave hits Seattle, Station 19 becomes a cooling center; 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.
Diane returns to help with Crisis One intervention training for Station 19 and Station 23 firefighters; Andy and Sullivan continue to be at odds; Jack helps a young autistic man on a city bus.
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; an explosion rips apart a neighborhood.
Station 19 and Station 23 attempt to celebrate Thanksgiving following the fallout from the neighborhood explosion; the firefighters come together to cook, toast to loved ones they have lost and celebrate the families they have become.
Vic and Jack lean on one another as they process the loss of Dean; Ben and Bailey try to convince Dean's parents to allow them to raise Pru; Andy's role temporarily expands; Carina and Maya explore growing their family.
It's the holiday season and the firefighters have their hands full responding to a number of crises throughout Seattle; putting aside their differences and personal drama, they come together to try and achieve a Christmas miracle.
Travis and Theo face danger while responding to an emergency at a haunted house; Ben continues his fight for Baby Pru; Vic opens up to Andy; Station 19 prepares to welcome patients to the Dean Miller Memorial Clinic.
The Station 19 crew offers aid to a man who sets himself on fire; Theo proves his devotion to Vic; Sullivan seeks advice from Dr. Webber; Travis comes to a realization about his love life.
Vic and Theo respond to a domestic disturbance between the parents of a transgender teenager; Jack learns shocking new details about his childhood; Ben and Travis help a clinic patient that's long overdue for medical treatment.
