After a luxury condo is robbed, the team is shocked to learn that not only was the family fast asleep when the crime occurred, but their teenaged daughter was violated during the invasion as well. Voight consults Jimmy from Firehouse 51 to confirm his suspicion that the family was knocked out by a powerful gas and Lindsay, Halstead, Atwater and Ruzek go undercover to seek out the perpetrators. Meanwhile, Voight tries to help a former acquaintance get back on his feet and Platt and Mouch receive disappointing news regarding their upcoming wedding.

Lindsay goes undercover in an effort to track down a rogue police officer targeting women leaving a local casino. When Detective Martin Watts, who oversees all cases out of the casino, gets word of the investigation he becomes involved much to Voight's dismay. After recent events, Burgess sets plans in motion to transfer Districts pending Platt's approval and Mouse attempts to lift Ruzek's spirits by offering to set him up with a friend. Meanwhile, Antonio volunteers to take Roman's place in the upcoming boxing match against Jimmy from Firehouse 51.