Firehouse 51 faces the fallout of the warehouse fire and the team welcomes a new crop of probies into the fold.

Violet and Novak grow suspicious of a mental health facility after treating an escaped patient. Severide feels heat coming down from HQ.

A mistake in the field lands a firefighter in the hospital. Herrmann looks to get one of their own back on track.

The FBI recruits Severide when an arson is staged to cover up the kidnapping of a judge's daughter.

Firehouse 51 responds to a complex hostage situation. Cruz continues to make strides. Chief Tomlin gives Severide an impossible task.

The probies take on their last day at Firehouse 51 when Kidd receives shocking news. Violet and Novak begin fundraising for the Joint Duty Program and receive a surprising donation.

Firehouse 51 responds when an old rundown RV explodes in a local neighborhood, injuring two people. Vasquez and Kidd discover something suspicious while investigating the cause.