To gain his trust, Ruzek (Patrick John Flueger) lets the target of an undercover operation drive his truck. Big mistake, as the target - with Ruzek riding shotgun - promptly drives through the front of a jewelry store, where a heist is already in progress. The target kills his (former) partners, takes the cash and jewelry, and gets away.
As he wasn't officially cleared at the time it went down, Ruzek's in hot water. He's relegated to desk duty while a special investigator handles his case.
After investigating the jewelry heist, the unit discovers it was an inside job. The thieves tunneled into the jewelry store after breaking into an adjacent restaurant, with the restaurant owners' son helping facilitate the operation.
But while the criminals are brought to justice, Ruzek isn't so lucky. As the investigation deepens, he is stripped of his police powers and forced to turn in his badge and gun.
As she preps to move into her own place, Lindsay (Sophia Bush) asks for Halstead's (Jesse Lee Soffer) help in finding a couch. After moving the couch into her apartment, they "test" it out; in the game of on again/off again, all signs point to on.