Darren Barnet

The unit investigates when several federal government employees succumb to symptoms of a heart attack. Meanwhile, Reid anxiously awaits his trial date.

Kate wrestles with her feelings following Toby's heart attack, Randall has to get used to his father's relationship with Jesse, and Jack and Rebecca must find a home that can accommodate their growing family.

Agents wonder if preserving the future as they know it is worth the destruction they could prevent.

With the suspects still at large and conditions worsening underground, first responders race against the clock to reach the trapped victims, while the investigation into the assailants comes into focus.

Chicago's first responders unite in the wake of a catastrophic gas explosion and fire that threaten a city government building. Herrmann reluctantly shadows Pascal while Violet, Novak and Dr. Frost take charge of triage efforts on site.