Backstrom and the team are investigating the case of an arsonists who is getting bolder with his criminal activities. The team's assistance is requested by the arson unit.
Backstrom is convinced that two fireman who bullied him as a child are the arsonists. He asks Gregory to help him investigate the case.
Gravely and Niedermayer go to visit an fire artist to gain insight into the mind of an arsonist. They stake out the scene of the fire and discover a young suspect.
Backstrom and Almond go to the fire station to pursue his theory about the D'Agostino brothers and discovers a canary in another fireman's law.
Valentine brings information about the underground to Backstrom. Valentine agrees to go undercover with Niedermayer to explore the lead so that Valentine does not lose his reputation.
Niedermayer poses as a private eye for the watch dealer to save Valentine's reputation.
Backstrom and Almond go to the fire station to confront the D'Agostino brothers about being thieves. Backstrom takes the opportunity to get some revenge on his childhood bullies and plant the watch on one of the brothers.
Backstrom suffers from a health condition. The EMTs are not willing to help Backstrom due to the confrontation with the fire department.
Almond comes to assist Backstrom in the middle of the night and the two have a heart-to-heart. Backstrom admits he was wrong and gets on board with Gravely's investigation. The team realizes that the arsonist investigator was lying the whole time.
The team confronts the arsonist investigator and gets her to confess to starting the fires. At the end of the episode Valentine and Backstrom go back to his hometown to find a childhood memento.