One Chicago: Your Exclusive Behind-the-Scenes Look at the Four-Way Crossover

Chicago Justicewill officially be welcomed into the #OneChicago family Wednesday night, as part of an epic three-hour crossover -- and TVGuide.com has your exclusive first look behind the scenes.

The crossover kicks off with a Chicago Fire episode involving a massive warehouse fire. The narrative moves to P.D. for the ensuing investigation, on the heels of the discovery that Olinsky's (Elias Koteas) daughter was in the warehouse at the time of the blaze. Finally, Justice steps in to prosecute the person believed to be responsible. (And all the while, the victims are being treated by the Chicago Medteam.)

"It's a story that is ripped from the headlines from the Oakland fire," executive producer Peter Jankowski tells TVGuide.com. "It's bigger than anything we've ever done on Chicago Fire before. It's also a little darker. It's a very, very somber subject matter."

The Justice part of the crossover features a guest appearance by Bradley Whitford (The West Wing) as a lawyer who faces off with Stone (Philip Winchester). "We had him in mind when [the part] was written," Jankowski says. "A lot of times we have people in mind when we write things. A lot of times we don't get that person. But it worked out in this case. And he's terrific."

After the crossover, Justice will move to its regular time slot, Sundays at 9/8c. Producers believe that launching it as part of the crossover will highlight the various links between all four shows.

"The One Chicago approach we have is sort of in tone, but when it comes to the actual execution ... CPD is the fist, Med is the heart, Justice is the brain, Fire is the crotch," Jankowski says. "Each show has a slightly different point of view. ... When you put them all together, you just come up with a slightly elevated project."

Check out the video to see stars from all four Chicago shows break down the logistics about pulling off a four-way crossover. (Hint: it's harder than it looks.)

The three-hour One Chicago crossover airs Wednesday at 8/7c on NBC.