Dawson confronts Chief Boden about his knowledge of Mills' father's death. Boden sternly cautions Dawson to stay out of it. Meanwhile, Severide talks with his father, Benny, over breakfast. Benny is equally reluctant to reveal any information to Severide.
On their first call of the morning, the squad responds to a restaurant fire. On the scene, Severide encounters the building's owner, who believes that someone set fire to his restaurant. Inside the building, a loose ceiling tile falls on Casey, engulfing him in flames. Cruz manages to pull Casey to safety in time. After the flames are extinguished, Otis discovers homemade fire bombs concealed in the ceiling. The fire seems to have been intentional.
Back at the station, Severide tells Boden that Benny wants to come by the station one more time. Boden tells Severide that Benny is not allowed in the station. Severide arranges to meet Benny at a different firehouse to appease Boden's request. Meanwhile, Dawson discovers that Mills has been looking into his father's death.
The squad tries to help Shay find a suitable sperm donor, but they're interrupted when Benny shows up with donuts. Boden pulls Benny aside and tells him to stay away from Firehouse 51, but Benny is not intimidated by the Chief. Afterward, Severide encourages his father to show some respect.
In the bunk room, Shay and Dawson discover Mouch's profile in the sperm donor database. Shay asks Mouch about the process of donating sperm, but they're interrupted when a call comes in. The squad responds to another restaurant fire with the same owner as the last one. Boden is starting to believe the owner's claim that someone is gunning for him. Behind the restaurant, Casey and Severide discover a homeless man who has been badly burned.
Boden, Casey and Severide decide to investigate the second restaurant fire, and Boden tells them to take Benny along. He may be a jerk, but he's an excellent arson investigator. Mills runs into Benny in the kitchen and asks about his father's death. Before Benny can say anything, Severide interrupts and invites his father to join in their investigation.
Benny and Severide investigate the burnt out restaurant. Benny rules out the homeless victim as the arsonist and determines that the culprit lit himself on fire during the arson. Boden calls the local hospitals and discovers a man who was admitted to a nearby emergency room with severe burns. The man tells Severide that the restaurant owner hired him to light the fires as part of an insurance scam.
Fed up with searching through sperm donor candidates, Shay asks Severide to donate his sperm so that she can have a baby. Meanwhile, Mills questions Benny again about his father's death, and Benny tells Mills that his father panicked in the middle of a fire, killing himself and another firefighter. Mills is upset by the news and he attacks Benny. Boden suspends Mills until further notice.
Meanwhile, Casey has Darden's widow, Heather, over for dinner and sparks begin to fly, but Casey tells Heather that he's not ready for a relationship with his best friend's widow. On his way out of town, Benny apologizes to Severide for creating problems at the firehouse. Severide visits Mills at his apartment and invites him to join the squad.