When Squad 3's transmission goes out, Squad  shows up to fill in. One of their members is Casey's childhood friend. He's loving his assignment, and tells Casey that his unit is like one big family, with him filling the roll of bachelor little brother. When 81 gets a call to a construction accident that 6 had been on, the arrive just in time to see flames erupt from the tunnel the team was working in. Truck scrambles to get the CFD brothers out safely. Matt finds his friend dragging his comrades out of the tunnel; he is the only that was unharmed. He and Casey manage to evacuate two of Squad 6's members, but the others, along with the construction crew victim, died immediately in the blast. Kannall insists that the explosion is his fault, but Casey suspects otherwise. His version of events just doesn't make sense with the timeline of the explosion. Casey confronts his friend with his suspicions, but Kannell begs him to stay quiet and let him take the fall so that his deceased CO doesn't take the hit. 

Sylvie and Gabby take different approaches to the retraining class they're forced to attend. They both end up passing with high scores. 

Kelly tries to figure out what he did to make Anna end things, but it's Stella who deduces that Anna's cancer is back. Anna pushes Kelly away when he visits her, but her dad stops by the firehouse and tells Kelly he shouldn't give up. Kelly brings a drawing from one of her patients and convinces her to let him stand by her as she goes through this.