The Season 5 premiere of Chicago Fire picks up the morning after the Season 4 finale ended, with Severide and Stella waking up together and being all cute couple-y. But just as audiences are adding her name to his list of love interests, she gets a message telling her that Grant escaped from Chicago Med. It's no surprise that he's then following her and threatening her before Severide fights him off - leading to what could be a fatal injury.
The whole team is called to a school bus accident where several kids are impaled by debris. New mother Dawson has a hard time seeing a child in pain and begins to doubt being a firefighter. She takes her fear to Casey and they ask Boden to transfer her back to being a paramedic. And Severide decides to move out in order to give the duo more space for their budding family, but that doesn't mean he wants to move in with his new girlfriend.
Meanwhile Borelli asks to go back to Truck 81, but when Boden tells him that he's not ready for the job it leads to a full-blown fight between them as Borelli files an official grievance against Boden, then publicly accuses the chief of getting his brother killed. Boden retaliates by suspending Borelli, leading Severide to show up on Borelli's doorstep and give him a talking-to while Boden is told that he must reassign the kid to 81.
And Susan Weller comes looking for Casey to apologize for coming on to him, but it's Casey with the surprise as he tells her that he wants to concentrate on being a firefighter - among other things. Plus, the guys wonder who's been writing romance fiction based on the team at the firehouse.