Chicago Fire, Chicago P.D., and Law & Order: SVUare coming together to find a multi-city serial killer, and when he possibly strikes again in Chicago, Halstead and Lindsey know exactly how to identify that the crime scene is his.

Mega Buzz: Who's going to die on Chicago P.D.?

The three-episode event begins on Tuesday, when firehouse 51 discovers that a woman they pulled out of a fire was actually brutally raped and left to die. In the second hour, Benson (Mariska Hargitay) travels to Chicago where she works with CPD to track down the man responsible for many past murders in New York under the Sergeant's tenure. But how did she know the cases were related? Watch the clip above to find out!

"There's something about the alchemy of these shows coming together that really makes it crackle," executive producer Matt Olmstead tells "This crossover is the best [crossover] yet and provided the best episode of Chicago P.D. yet. The cool thing about this one is ... that it starts in Chicago and stays in Chicago in the 9pm hour with SVU people over there. Then, at 10, it goes to New York with our guys going there. So it plays like a 3-hour movie without ping-ponging back to particular cities for the timeslots."

Three three-show crossover kicks off with Chicago Fire airs on Tuesday at 10/9c, followed by Chicago P.D.on Wednesday at 9/8c and then Law & Order: SVUat 10/9c on NBC.