The episode picks up immediately with Squad 3 (Severide, Cruz, Capp, and Tony) trapped in a capsized boat. They manage to escape, but Cruz is found unconscious and requires CPR from Casey. While physically fine, Cruz begins struggling with PTSD from the near-death experience.
For a complete look at the events and character arcs throughout this season, you can watch this recap of Season 10: Chicago.Fire.10x01.Mayday.m720p.AMZN.WEB-DL.DD2...
Severide informs his mother of his engagement to Stella, but she reacts negatively, suggesting the marriage is destined to fail like his father's. The episode picks up immediately with Squad 3
The couple tries to keep their new relationship secret, but the crew at 51 reveals they have known for some time, leading the pair to go public. but she reacts negatively