David Eigenberg, Christian Stolte

Law & Order and its many spin-offs have long been known for ripping from the headlines, whether it was the flagship series' fictionalized version of Mel Gibson's anti-Semitic rant or SVU's take on the Trayvon Martin murder. It was only a matter of time before Dick Wolf's newest series, Chicago Fire and  Chicago P.D., followed suit. In a special two-part crossover airing on Tuesday and Wednesday at 10/9c on NBC, the shows will focus on a hospital explosion that bears a striking resemblance to the Boston Marathon bombing. What can viewers expect from the shows' biggest episodes yet? Read on to find out:

1.  A new leader in charge: As we first teased in this exclusive sneak peek, it's finally Herrmann's time to shine after he passed his lieutenant's exam earlier this season. His initial doubts about suddenly playing top dog couldn't come at a worse time, since Firehouse 51 is first on the scene to the explosion, natch. Although Herrrmann (David Eigenberg) will be the one calling the shots alongside the Chief (Eamonn Walker), Lt. Casey (Jesse Spencer) will still make a big dent in the immediate recovery effort, and particularly when another member of 51 is in danger.

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2. One of their own caught in the crosshairs: That's right. In addition to trying to put out subsequent fires from the explosion and search for missing victims, 51 will also have a deep personal investment in getting the debris cleared out when one member from the house goes missing and is believed to be buried underneath the rubble.

3. A few familiar faces return: Days after reprising his role as wife killer Colin Sweeney on The Good Wife, Emmy nominee Dylan Baker will be back on Fire — this time to save lives. In his second appearance as the icy but dedicated Dr. Arata, Baker's character is one of the first to operate on a possibly fatally injured victim. Shay's old EMT partner, Rafferty (Christine Evangelista), will also be back to lend a hand and treat the many, many people injured.

4. Some new blood: Fresh off her six-year run on The Mentalist, Amanda Righetti pops up early in the episode as Holly, a pediatrician who just moved to the Windy City from New York. Her character, who also appears on Wednesday's episode of P.D., blends in well, and quickly, with the rest of the team — which is no small task considering the size and scope of the two casts.

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5. An imminent threat: While most of 51 will be dealing with the aftermath of the explosion, Mills (Charlie Barnett), Cruz (Joe Minoso) and the Chief must go on the offensive and try to hunt down a possible second bomb. Will that rescue squad training come in handy? Only time will tell.

6. A Chicago P.D. breakout: The police department, and specifically Voight's intelligence unit, will appear quickly on the scene to figure out what, or who, caused the explosion. However, it's another officer from the NBC spin-off — Kim Burgess (Marina Squerciati) — who delivers a breakout performance during the first hour. Like so many of her P.D. co-stars who have used crossover appearances on Fire to unpeel new layers (see: Voight's battle with Casey over his son in Season 1, Halstead's complicated romantic relationship with Dawson at the beginning of Season 2), Squerciati shows Burgess' vulnerable side when her niece is seriously injured in the bombing and delivers an emotional performance that tugs at the heartstrings.

7. A big cliff-hanger: The first hour will resolve several burning questions, but there are also a few cliff-hangers left unanswered at the end of the first hour. Chief among them is the health of one of Firehouse 51's own that will surely have viewers on the edge of their seat for most, if not all of Wednesday before P.D. picks things up.

The two-night event kicks off on Chicago Fire on Tuesday at 10/9c on NBC. Watch the latest episode here.