Here's the synopsis: When a gas explosion rocks a high-rise building, Chicago's first responders spring into action to save hundreds of citizens. However, the disaster beneath the surface sends our heroes on a race to rescue 40 people trapped deep underground, including two of their own.

“Putting together what is essentially a three-hour action movie is an incredibly ambitious task requiring complete coordination across our writers, casts, crews, and producers, along with help from the city of Chicago,” shared Anastasia Puglisi, Wolf Entertainment Executive Vice President and co-executive producer of the #OneChicago series. “We’re thrilled to have the best talent in every department to meet this challenge, reinforce the #OneChicago brand, and provide our fans with a unique and compelling viewing experience.”
Chicago Med stars S. Epatha Merkerson, Oliver Platt, Steven Weber, Marlyne Barrett, Jessy Schram, Luke Mitchell, Sarah Ramos and Darren Barnet. Executive producers are Dick Wolf, Allen MacDonald, Stephen Hootstein and Peter Jankowski.
Chicago Fire stars Taylor Kinney, Dermot Mulroney, David Eigenberg, Miranda Rae Mayo, Joe Miñoso, Christian Stolte, Daniel Kyri, Hanako Greensmith, Jake Lockett and Jocelyn Hudon. Executive producers are Dick Wolf, Andrea Newman, Reza Tabrizi, Matt Whitney and Peter Jankowski.
Chicago PD stars Jason Beghe, Patrick John Flueger, Marina Squerciati, LaRoyce Hawkins, Amy Morton, Benjamin, Levy Aguilar and Toya Turner. Executive producers are Dick Wolf, Gwen Sigan, Rick Eid, Chad Saxton, Gavin Harris, Jason Beghe and Peter Jankowski.
The One Chicago crossover airs Wednesday, January 29 from 8:00 PM to 11:00 PM on NBC.