Tracy Spiridakos

Angus "Mac" MacGyver (Lucas Till) and Jack Dalton (George Eads), special agents for the Department of External Services (DXS), join forces to recover a missing bioweapon that has the ability to destroy hundreds of thousands of people with one single drop.

When Lindsay (Sophia Bush) receives a panicked call from her mother Bunny (guest star Markie Post) whose boyfriend had just been shot, Lindsay must figure out the best way to approach the situation, as her mother is now a murder suspect. The case opens up when a group of high school students OD, and the drugs in question relate back to the situation with Bunny. In addition to her mother's issues, Lindsay finds herself up against the review board dealing with consequences of her actions.

Kidd and Severide's honeymoon is interrupted by a dangerous person from their past. Kidd's former academy classmate joins Firehouse 51. Brett and Violet reflect on their relationships.

A live video is streamed online showcasing a tortured man being beaten and burned alive. Upon further investigation, the victim's identity is traced back to that of a man who had been previously locked up for statutory rape. When another attack of a similar nature occurs, Intelligence finds a connection between the crimes, suspected pedophiles, and group named the Perv Hunters. Meanwhile, Lindsay (Sophia Bush) runs into a few bumps in the road both personally and professionally.

When the team is called to an in progress bank robbery, they come across Detective Hailey Upton (guest star Tracy Spiridakos) trying to take over the crime scene with her Robbery Homicide unit butting heads with Voight (Jason Beghe) in the process. As the robberies continue to be executed around the city, Lindsay (Sophia Bush) is forced to make a decision in the heat of the moment, revealing a surprising suspect behind the mask. While working on the case at the district, Upton is shocked to come across Platt (Amy Morton), who has a special connection to her past.