Internal Affairs grills a stoic Voight on whether he has information on the murder of Sheldon Jin - Voight firmly denies any knowledge. He faces the same kind of criticism back at District 21, with Halstead the chief proponent of making Intelligence the lead on Jin's case. Just about the only person without an opinion is the new office secretary - Nadia, the ex-junkie Lindsay helped get clean.
To complicate matters, Halstead receives a mysterious package that contains a message from Jin sent before he died. Inside is a thumb drive that, among other things, reveals Jin worked with IA. After some discussion with Lindsay, he takes the drive to Voight who then confronts Stillwell. He warns Stillwell that Jin recorded every meeting between them and that the thumb drive holds every threat Stillwell made, solidifying his guilt. Unfazed, Stillwell counters with a promise to Voight - exposure. How would his team react if they knew he worked with IA? The men appear to be at a stalemate.
Meanwhile, Antonio hits up an informant, Jellybean, for intel on a major bust opportunity for the team. All she gives them is a time and a place, but Antonio vouches for her reliability and they set up an undercover sting to intercept an armored van. Things go south fast at the location - a truck rams into Voight's car and thugs emerge from every direction, guns ablaze. A second car rolls up and cleans the van out while Ruzek manages to drop one of the shooters.
As the team reels from the botched move, a DA visits Voight and Olinsky with more bad news - turns out that van held evidence that was going to convict a career Chicago criminal, Oskar Bembenek, and he hired out to have the van hit. With help from Burgess and her new partner Officer Sean Roman - a transfer from another district who reveals he fell in love with his ex-partner, a female cop - Intelligence tracks down one of the hired hitmen and learns he kept the evidence in lieu of a payday from Oskar.
The team uses this as an opportunity and stages the exchange, only after Oskar verifies the evidence his men pull out guns. Another shootout occurs and this time Halstead is forced to kill one of the men right in front of Oskar. Problem is, he was Oskar's brother. Oskar locks eyes with Halstead as the bracelets come on, revenge in his eyes...
Lindsay takes the break in action to follow up on a series of ignored calls from a woman named "Bunny" - aka, her mom. She bristles during a quick meeting at Bunny's bar, clearly not on good terms, and demands that she contact her via email from now on, even after Bunny announces that she's about to get married.
Later, Halstead pressures Voight for an answer on Stillwell, but Voight won't give an inch - or return the thumb drive. In turn, Halstead questions Lindsay's resolve regarding Voight, certain that their leader is burying the case.
And that might be exactly what Voight intends to do - until Jin's mom Susan visits him. She thanks Voight for helping her son realize his dream of becoming a cop. This convinces Voight to take Jin's evidence to Commander Perry and leads to Stillwell's arrest - and the subsequent outing of Voight as his secret contact.
The allegations send Voight to headquarters, where Perry demands his badge and gun. But after a moment alone with another police chief, Voight reveals that the transcripts from the thumb drive vacuumed up other sensitive material, and with one look at a printout the chief goes pale, clearly aware of an indiscretion he wants to remain undetected.
Exonerated, Voight pulls out cash from a secret safe and meets up with Jin's father. He hands the man the money with explicit instructions - pay off the gambling debt. Antonio makes a similar arrangement with cash lifted from the Oskar sting. He brings 10 percent to the registered informant, Jellybean. It amounts to 20 grand and she cries tears of joy - it will allow her to leave the city. She kisses Antonio on her way out.
The whole team is stunned to learn Voight beat the charges, especially Lindsay. Olinsky interrupts and pulls Halstead aside. An informant tipped him off - Oskar just put a $100,000 bounty on his head for killing his brother.