POLICE LOG: A copycat killer may be emulating the man who kidnapped Officer Gail Peck and murdered Detective Jerry Barber. Detailed report follows:
A worried dad believes something is seriously wrong when his 23-year-old daughter, Grace Finn, goes missing. It's only been nine hours, so there's nothing the police can do at the moment. In other news, Andy and Nick chase down a cab that's driving down the road with a man on the hood. The guy is a store owner who was trying to stop a joyriding kid. Surveillance footage shows that the cab was used earlier for a more nefarious purpose. A man knocked out a woman and kidnapped her. The victim is Grace Finn. The cab was formerly registered to the man who kidnapped Gail and killed Detective Jerry Barber.
Luke Callahan returns to 15 to work the case. This may be a copycat of serial killer Ross Perik. That means the team has less than 24 hours to find this missing girl. Traci is assigned to work with Gail's brother, Steve, in guns and gangs for the day, so she's unaware of what's happening. Sam is a bit on edge, so he asks Andy to partner with him. As for Gail, she bears the brunt of the anger and fear being felt by Grace's dad. She doesn't reveal that she was a kidnap victim of the man this copycat killer is trying to emulate.
Oliver and Dov have a discussion with a neighborhood watch dad who wants to know what happened regarding the missing girl. Elsewhere, Sam clutches Jerry's watch as he and Andy track down the person who bought the cab after Perik. The sketchy guy is guilty of neglectful care of his elderly father, but he's not the kidnapper. He sold the cab to an unknown buyer. Luke thinks talking to Perik may help. That's not gonna worked for the incarcerated killer. The only person he'll talk to is his former kidnap victim, Officer Gail Peck.
After Gail has a heart-to-heart chat with Grace Finn's dad, she volunteers to meet with the man who abducted her. Perik is giddy when he sees Gail. He wants something from her before giving up any information. He wants her to reveal the secret she's been keeping. He can see the guilt on her face. Gail complies by telling the tale of how she killed a cat when she was a kid. That's not enough for Perik. He wants more. Gail obliges by letting him know she cheated on her boyfriend because she was jealous. Perik gives her the info she seeks. Gail exits the interrogation room to find Nick on the other side. He heard everything.
Dov and Oliver realize that the neighborhood watch guy they spoke with at the crime scene is actually the kidnapper they are seeking. Thanks to Gail's chat with Perik, they are able to ID the kidnapper as a recent parolee. Grace Finn is found at the guy's home. The suspect is arrested and Grace's relieved dad gives Frank a big hug once he learns his daughter is safe.
In random news, the officers of 15 are caught off guard when Frank announces that Chris worked his last shift without saying goodbye. Chloe reveals to Marlo that Dov accused her of being bipolar. Speaking of Dov, he's hurting because Chris is gone. But he only accepts an offer to drown sorrows at the Penny when Oliver reveals he needs a friend. He's getting a divorce because his wife is in love with someone else. Speaking of falling for another, Nick admits that he never intended to have feelings for Andy. It was a crush that never went away. He says all this just before he asks Gail to exit his car.