Firehouse 51 responds to the scene of a single-car accident, but tensions flare when Firehouse 20 arrives on scene and Capt. Delaney wants to take command.
Things only get worse when a bed bug infestation forces 51 to camp out at 20 for the remainder of the shift.
However, a life-and-death situation causes both firehouses to see things in a new light after Casey and Gallo rescue two firefighters from 20 during a dangerous call.
Gallo and Violet continue to hook up, though both deny that they are in a relationship.
Brett, Kidd, and Foster are afraid Capt. Leone will want payback for them closing down the women's only lounge at 51.
Though Leone is nothing but nice, they still fear she will try something. They later learn Leone's plan was to make them miserable by having them be afraid she would do something.
Boden attends a meeting and is reintroduced to Mike Buckley, a firefighter he trained at the academy 10 years ago.
Buckley reveals he only has a few months left to live, stating his continued exposure to carcinogens as a firefighter caused his cancer.
Boden takes the cause to heart and decides to raise awareness for the dangers surrounding firefighting.