'Arrow' Season 4 SPOILERS: Annual 'The Flash' Crossover, 'DC's Legends of Tomorrow' Intro

Arrow featured a crossover of sorts with its latest Season 4 episode, "Haunted," that featured an appearance by Matt Ryan as John Constantine from the cancelled NBC show of the same name. However, the annual crossover between Arrow and The Flash is quickly approaching, and we've got some spoilers on what to expect, specifically how the episode sets up and introduces DC's Legends of Tomorrow.

Deadline spoke to executive producer Marc Guggenheim about the upcoming crossover, and he revealed how this year's version will be different from the inaugural one last year.

"There’s a lot of things that are really cool about this year’s crossover, one of which is the fact that there really is a true 2-part story unlike last year where it was two interconnected episodes where each had their own beginning, middle, and end," he said.

Last year, the Arrow crew traveled to Central City in search of a villain named Captain Boomerang and wound up helping Barry Allen (Grant Gustin) and his team take down the Rainbow Raider, who turned Barry into an angry speedster until Oliver knocked some sense back into him.

Then, the Flash crew arrived in Starling City (now Star City) to help Oliver (Stephen Amell) take down Captain Boomerang. The two episodes were somewhat linked, but not totally. It seems like that will not be the case, however, this season.

"This is a big two-part event, one single bad guy, and it will very clearly launch Legends Of Tomorrow," Guggenheim said. "But at the same time what I think is a lot of fun about it is that it doesn’t feel like a backdoor pilot for Legends Of Tomorrow. It feels like an episode of Flash and then an episode of Arrow. It truly is a 2-hour Flash/Arrow event that just so happens to introduce us to some new characters who will be a big part of Legends Of Tomorrow."

Could this crossover introduce Vandal Savage, the main villain of the spinoff?

What do you think of these spoilers? Let us know in the comments section below.