Upton and Halstead wake up in bed together. They're making plans for their day off, but things take a sour turn when Halstead tells Hailey that he loves her.
She panics and "remembers" that she has to take her car to the mechanic.
After bolting from her own apartment, she picks up a nearby missing person's call.
When she rolls through, she realizes that something strange definitely happened to the Carlton family and calls in for backup.
Intelligence arrives with Halstead in tow.
A neighbor explains she became worried when she hadn't seen the family in a few days.
Kim realizes that the man living in the home was using the stolen identity of Ray Carlton, who actually died four years ago.
The situation gets even hazier when it's revealed that there's no paper trail for Ray and Helen's daughter, Becca, who wasn't even enrolled in school.
The Carlton's are far from the perfect family that the neighbor considered them to be, though she admits that both Helen and Becca seemed afraid of Ray and not very independent.
This leads Intelligence to believe that maybe it was a situation of abuse.
A further investigation reveals that Ray was your run-of-the-mill conman who would skip town after scamming someone.
After getting a hit on Ray's debit card, they find footage of him clearing out his bank account. Becca looks scared.
The video also reveals a man kidnapped them, which leads Intelligence to believe that, this time, he conned the wrong man.
Hailey is very emotionally invested in the case and takes great interest in Becca as the situation reminds her of her own toxic childhood.
She realizes that both Becca and Annie, the daughter of the next-door neighbor, have the same flashlight. A quick chat with the young girl reveals that she was really close with Becca. They would use the flashlight whenever she was in danger and needed to sneak away.
Eventually, Annie reveals that she knew what happened to the Carlton family.
They bring her in for questioning where she admits to seeing a man break into the home and lead the family out to an old station wagon.
Intelligence is able to trace the station wagon to a man named Alejandro Jimenez.
They also find Helen's body buried under a mount of snow with her teeth pulled out and her fingers burned off so that no one would be able to identify her.
After finding Alejandro's mobile home, Hailey ignores Voight's orders and ambushes the man on his property after seeing him with a gun.
They check his trailer and the shed, but find no signs of Ray or Becca other than the girl's sweater.
Voight isn't pleased with Hailey for ignoring his orders. She's passionate about the case, but he wants to approach it with a clear head.
Hailey brings in Annie, who struggles to identify Alejandro, but does so with a nudge from Hailey.
Eventually, Hailey realizes that Alejandro's place is on the edge of industrial land, which means there are plenty of tunnels underground. She realizes that she and Halstead arrived just as he was going to kill Ray and Becca.
Intelligence grabs back up and they go search the property again. Hailey finds a trap door under the snow, and when she goes underground, she finds the father and daughter unconscious.
Ray is no longer alive, but Becca still has a pulse.
After the emotional case, Hailey questions if she's unfit to be a cop because of how much cases like this remind her of her toxic childhood.
Voight informs her that what makes her a good cop also makes her a bad cop, but she does this to help all the other helpless little girls.
Jay swings by Hailey's house, who opens up about her past trauma. She explains that she got freaked out when he said the L-word because, in her house, it was usually followed by an apology.
She informs him that she's not good at relationships and intimacy, but she wants to be because she loves him.
Jay listens and promises that he's not going anywhere.