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. The annual Phoenix Festival brings out some reckless behavior in some of Seattle's citizens, challenging the teams at Station 19 and Grey Sloan Memorial.

Andy and Sullivan's relationship continues to be tested. Meanwhile, Emmett joins Dean and Vic on a mental health call, and Maya does some soul searching.

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

Diane returns to help with Crisis One intervention training for Station 19 and Station 23 firefighters. Meanwhile, Andy and Sullivan continue to be at odds, and 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, while Dean considers a new potential career opportunity. Meanwhile, an explosion rips apart a neighborhood and changes the lives of our firefighters forever.

Station 19 and Station 23 each 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 while Ben and Bailey try to convince Dean's parents to allow them to raise Pru. Meanwhile at Station 23, Andy's role temporarily expands and Sullivan subs in. Carina and Maya explore growing their family

It's the most wonderful time of the year 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.

A new chief starts at Station 19. Meanwhile, the crew responds to a young girl seeking help and a call about an SUV flown over a cliff.

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; and 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; and Travis comes to a realization about his love life.

The Dean Miller Memorial Clinic has its opening day. Meanwhile, Sullivan gives Beckett an ultimatum, and the crew responds to a skydiving incident.

Through a series of flashbacks, Sullivan and Natasha's past is revealed. Meanwhile, Ben and Bailey have a discussion with Pru's grandparents, and the crew responds to a fire at a candy factory

The crew at Station 23 faces a difficult goodbye. Meanwhile, Andy meets a charming firefighter, and Emmett invites Travis to have dinner with his parents.

Andy deals with the aftermath of a trauma.

Andy's fate remains unknown as a trial date is set. Meanwhile, Vic and Sullivan are approached by an unexpected guest, and the crew responds to a row of townhouses on fire.

Vic and Theo respond to a domestic disturbance between the parents of a trans teenager; Jack learns shocking new details about his childhood, and Ben and Travis help a clinic patient that's long overdue for medical treatment.

Andy tracks down a witness to testify at her trial. Meanwhile, Carina and Maya deal with a stressful situation, and the crew responds to a car wreck.