Chicago P.D. Episode 2.20 The Number of Rats

Picking up right where Chicago Fire left off, Sergeant Benson from New York City's Special Victims Unit joins Voight and the rest of P.D. at Chicago Med. They question Victoria, the severely burned victim, and her devastated sister, but neither can offer any evidence or detail that could lead to a suspect. The detectives return to District 21 knowing only that every victim reported the same description of her assailant: a man in a medical uniform with his arm in a sling. They also know that each victim had her nails painted green, although the horrific severity of Victoria's burns prevents them from identifying if the man painted her nails. To make matters worse, Victoria passes away soon after the brief interview.

Voight makes sure Intelligence opens a hotline, and Nadia finds herself fielding a nonstop series of calls while attempting to organize a surprise birthday for Lindsay. Detectives Amaro and Fin fly up from SVU to provide insight from the previous cases and help on the hunt, with their first stop a revisit of the crime scene. Lieutenant Casey from Firehouse 51 guides the detectives, along with members of Intelligence, through the remains of Victoria's apartment. A thorough search reveals a missed piece of evidence: a small bottle of green nail polish. There's no doubt now that this is the same killer from Benson's open case.

Meanwhile, Benson discovers that Halstead's brother (and new member of the Chicago Med staff), Will, knew one of the victims in New York and that detectives questioned him during the initial investigation. Could he be the killer? After Benson approaches Voight with the news, he agrees to help ambush Will for an interrogation without Halstead's knowledge. Except when they bring Will in, Halstead finds the situation suspicious and stops the ruse despite Will's insistence on innocence and his willingness to cooperate.

Later, the hotline pays off with a lead that describes the killer just like the other victims - arm in a sling and wearing scrubs. Mouse pulls security cameras in Victoria's neighborhood and snags an ID on a car that matches a witness' statement. Burgess and Roman track it down and arrest the driver, Greg Yates, on dubious charges in order to place him in the sights of Intelligence. Yates withstands intense scrutiny from Lindsay and Amaro - and emits his own creepy, confident vibe - but without any evidence to back up their hunch, they release him. Voight orders Intelligence to dig into Yates with everything they've got - until Will, now no longer a suspect, steps in with additional information. Turns out Yates served as one of Will's professors in New York and, at a bar one night, Yates corned Will and unleashed a series of unsavory comments about several of the female students in Will's class - including a future victim. Before Intelligence can pounce on the details, Yates contacts Lindsay and asks to meet her (and only her) in public. Lindsay agrees to his terms - and Voight organizes a detail team to verify her safety.

Before Lindsay heads out, Benson calls her with sound advice: be ready and be careful. Calm and collected, Lindsay meets Yates in Millennium Park that night. He leads her away from the park and toward the Art Institute of Chicago, forcing Intelligence to scramble in an effort to keep her covered should Yates make an unexpected move. Instead, Yates rambles to Lindsay about "unintended consequences" and gives Lindsay neither a new clue nor a confession. She leaves confused - what was the point of their meeting?

Yates' motivation becomes clear moments later when Boden calls Voight to announce the discovery of another body. The Firehouse 51 chief shows Intelligence, Fin and Amaro the charred remains of an apartment and a corresponding victim with a familiar bottle of green nail polish nearby. This means Yates met with Lindsay to guarantee plausible deniability - the perfect alibi. Mouse traces Yates' phone to an empty apartment, but when Intelligence barges inside all they find is his cell phone.

And that's because Yates is halfway around the city stalking the last person on anyone's mind: Nadia. She corrals a cake in honor of Lindsay's 30th birthday, exits the car - and Yates clocks her with a tire iron. When Nadia collapses, unconscious, Yates stuffs her in the back seat, then restarts the car and drives away. As the car peels out, Lindsay's cake lays in the street - the only evidence of Nadia's abduction.