After being forced to take time off work to recover from his surgery, Owen finds himself immersed in the search for a serial arsonist. Meanwhile, T.K. and Carlos take their relationship to the next level and Marjan copes with the aftermath of losing someone on the job.

A recovering Owen becomes the prime suspect in the serial arsonist case. Meanwhile, T.K. and Carlos find themselves in a fiery situation and Tommy gets the surprise of her life.

Owen, Tommy & the 126 race to the rescue when a medieval-themed restaurant suffers a case of carbon monoxide poisoning. Meanwhile the crew is worried that Paul still has not mentally recovered from his surgery and his friendship with Marjan is over. Mateo is offered a promotion by his old fire captain, but quickly realizes he is not the man he once knew.