12x11 - Chicago P.D.

When a gas explosion rocks a high-rise, Chicago's first responders come out in force to rescue hundreds of civilians. It's the calamity beneath the surface, however, that sends our heroes on a race to save 40 people trapped deep underground, including two of their own. The crossover starts on Chicago Fire S13E11 In the Trenches (I) and Chicago Med S10E11 In the Trenches (II).