Lindsay brings Justin by the boxing gym to meet Halstead and Antonio, and as per usual Voight's son makes another indelible impression by flashing attitude, jealous of the Halstead's rapport with Lindsay. Voight himself echoes the sentiment to Halstead later and declares Lindsay "off limits" - a decree she takes personally and bristles with Voight over in private. He remains firm - if she wants to date a cop, she can go look at another district.
A call sends Voight out to an arrest in progress - it's Maurice, his shady contact that gives him money to keep police off his back. After Voight instructs the arresting officer to release Maurice, he slaps the criminal and demands he get paid the full 5K for the service. Disrespected, Maurice offers 2K - Voight rejects it and issues a deadline. He wants the full amount in his hands by the end of the day, or Maurice can forget about police protection. Later, Grandishar demands compliance from Voight and requests - again - for the kind of bust he promised her. She wants Maurice; he leaves without a guarantee. This leads Grandishar to approach another detective - Antonio. Will he accept her mysterious play for alliance?
Back at District 21, Platt assigns Burgess and Atwater a slick, brand-new patrol car - and warns them it better stay that way, too. Their afternoon cruise comes to a halt when they investigate a crazed, bloody woman roaming the sidewalk. She assaults Atwater with a broken bottle, knocking off the car's side mirror and forcing Burgess to subdue her with a Taser. Once she lands in the hospital, the real shock comes - this woman suffered from a cocaine-induced psychotic break after a balloon of cocaine exploded in her stomach. She defies the drug mule standard, but it can't be denied - she's lucky the other 29 balloons stayed intact.
Lindsay and Halstead question the young woman, and she reveals three partners - all undergrads, all girls, all carrying balloons full of cocaine for two known drug smugglers, Sean and Brendan Collins. Once Intelligence comes up empty on dorm searches, they get the jump on Brendan and spark a high-speed chase, certain he knows the whereabouts of the others. Unfortunately, Brendan takes a wrong turn and wrecks his van, killing himself instantly. Even worse, his van's clean - no drugs and no drug mules.
Meanwhile, Atwater and Burgess ride their busted patrol car to local mechanics and ask for a favor. In return, the mechanics want $500 cash, money Burgess struggles to borrow from a friend when another call forces them to rush - on foot - to a corner store theft. It proves bogus - the "thief" only tried to steal a loaf of bread out of desperation - and Burgess lets the suspect go after buying her the loaf of bread. Turns out, the woman is related to one of the mechanics, and he gives the officers a discount out of gratitude.
With the main case at a standstill, Voight pulls one last play and takes Halstead to a bar frequented by Brendan and Sean's uncle. With a little of Voight's patented brand of rough interrogation, the uncle gives up Sean's location. Sean gets wind of Intelligence and leaves before they arrive, but they do find one of the undergrads - dead on a table, disemboweled.
Jin snags a new lead from cellphone records and IDs one of Sean's dirty associates - Porter, an EMT who makes money on the side by patching up gang bangers. Sure enough, Olinksy and Ruzek spot him during their rooftop stakeout - and watch him lead Sean and the last two drug mules into a tattoo shop. Ruzek rushes in against orders, seconds after Porter cuts open one of the girls. Chaos ensues - the other girl starts to OD, and one of the thugs escapes, detained in an alley by the nearest police backup, Burgess and Atwater. Voight congratulates the young officers, and they return to their patrol car in high spirits... until a cement block drops from above and dents the vehicle. So much for staying on Platt's good side.
A few hours later, Ruzek swings by Olinsky's garage to apologize for disobeying orders. Olinsky rips into him, furious that Ruzek continues to act on instinct - and tells him to look for a new job. Something cushy, something where he won't threaten their lives. Either way, he's not ready for Intelligence.
Another post-shift meeting takes a surprise turn when Voight stops by Lindsay's apartment with a rap sheet on a guy he noticed hanging around Justin, a supposed "friend." She offers to handle it and goes back inside - to join Halstead. Both casual, flirtatious, winding down their night with a drink. Is there something between them? It certainly seems that way...