An Agent of the Machine (S05E12)

The team is on high alert when a previous incident during a fire call leaves a dangerous man on the loose with a vendetta to target Lt. Casey (Jesse Spencer) and Firehouse 51, and prompts CPD to step in. Dennis Mack (Nick Boraine), a buddy firefighter of Severide's (Taylor Kinney) father, comes to town to shadow the squad but may have ulterior motives. Meanwhile, Brett (Kara Killmer) and Antonio's (Jon Seda) relationship hits some bumps in the road when his ex-wife Laura (America Olivo) surfaces and Casey has a present for Dawson (Monica Raymund). (iTunes)