While responding to a fire at a cartel owned house, Stella and Cordova get separated from one another. Later, Gabby and Sylvie respond to a car accident that was caused by the same cartel -- apparently some money went missing during the fire and the cartel is determined to find the thief, no matter the consequences. Antonio gets involved, and Cordovo seems like the most likely suspect amongst the firefighters. Casey makes the mistake of confronting him about the incident at Molly's, which only raises tensions. He apologizes the next day when he and Boden have an informal talk with the floater. Cordova reveals that he saw a "ghost" in the fire, and went after the supposed victim but was unable to locate anyone. Cordova asks Gabby to find out if his career is on the line, and she points out that if Casey doesn't trust him, he only has himself to blame. Matt and Kelly go over the blue prints for the house and realize there's a dead space or "trap." They take Cordova back to walk through the house and find the secret space. When they open up the false bookcase, they find a dead cartel member with the money stuffed in his pockets. Matt apologizes again for doubting the new guy, and then reassures Cordova that he'll request him for any more permanent opening that may come up. Cordova later visits the Casey residence and tells Matt thanks but no thanks. He passes it off as having a rocky start at 51, but it's clear to Gabby that it's because he's not over her and he's backing off to make things easier. Gabby and Matt reconcile and reaffirm their relationship.
Coming off of Jennifer's inappropriate and bizarre warning, Stella is shocked to find out that Kelly has been married before from Sylvie. When she confronts him about it, she's even more unsettled by the circumstances of his marriage and the fact that he's been engaged before as well. She ends up deciding to move out of his apartment so that their relationship can progress at a more normal rate. She's afraid that she's offended Kelly and that things might be over, but stands firm in her decision. Kelly shows up at her new place, and their relationship moves forward.
Herrmann has decided that Lee Henry needs some practical life lessons, so when his son approaches him about living in the apartment over their garage, Christopher agrees on the condition that Lee Henry pay rent, etc. He hires his son to work as a stock boy/busser at Molly's. Herrmann is impressed with the boy's work ethic, but Stella warns him that kids that age only behave so well when they're trying to get away with something else. Lo and behold, Cindy shows up at 51 during the next shift and reveals that she caught Lee Henry watching porn in the apartment. Herrmann uses this as another teaching moment, revoking the boy's apartment privileges and forcing him to do KP duty at the fire house.
Otis has been working his ass off getting ready for a FD assessment, but apparently he was working too hard -- he not only failed, but was told that he'd actually lost ground. Otis starts to take a fatalistic attitude about his chances at 51, letting Cordova know that he approves of him as a replacement. He visits Casey and sings Cordova's praises, saying that one of the things he's learned at 51 is that the team is more important than the individual. He says that if he fails his next assessment, he'll ask for the hold on his spot at 51 to be released. Everybody encourages him to stay positive, and before he heads in for his assessment, he gets text after text from the team at the firehouse wishing him luck.