A young man named Nathan is found badly beaten in the trunk of his car, but the Intelligence Unit must desperately search for his fiancee Sarah, who has gone missing in the aftermath of the attack. They meet initial resistance from the neighborhood locals, who think that CPD is more concerned with finding a Caucasian woman than helping anyone of color.
But when they recover Sara's cell phone, the teenager who has it tells Ruzek that he saw Nathan speaking with known drug dealer Michael Hudson, who tells Voight that Nathan was buying drugs from him with counterfeit money. Confronted by Lindsay Nathan admits to the deal and says he was jumped, which just creates more reasons for someone to harm Sara.
A breakthrough comes after Voight learns someone has footage of the night on tape and her captor is easily identified as Kenneth Waddell. But he's holed up in the most dangerous neighborhood in the district so Voight and his team wind up reaching a peace with the residents to catch their suspect and save Sarah.
Meanwhile, after Halstead (Jesse Lee Soffer) surprised Lindsay (Sophia Bush) by asking her to move in with him in Season 4, Episode 1 she returns the favor by springing a question on him. She would rather that he move in with her and he agrees. Halstead gets another bomb dropped on him when Craig (Samuel Hunt) says he's considering returning to the Army Rangers.