'Arrow' Season 4 SPOILERS: Details on 'The Flash' Crossover from Stephen Amell, Grant Gustin

The annual crossover event between the CW's Arrow (currently in Season 4) and The Flash (currently in Season 2) will air on December 1 and 2, and this year's event will set up the new spinoff DC's Legends of Tomorrow. We've got spoilers and details from the mouths of stars Stephen Amell and Grant Gustin, so let's not waste any time.

TVLine spoke to the actors during a set visit last month, and Amell did not pull any punches when describing the two episodes. “These two crossover episodes standing together will probably be, in my mind, the pinnacle achievement for both shows,” he said.

“It feels even bigger,” Gustin added. “I feel like more people are a part of it this year from both sides, and we’re tying in Legends, obviously, so it’s just bigger.”

Last season's crossover was received well by critics and fans alike, so it's good to know that this one is shaping up to be even better. Moreover, the two episodes are far more connected than last year's, which functioned as two loosely linked standalone hours.

"It's not the case this year," Amell said. "If you put them back-to-back on one night, they would run like one two-hour episode of television."

To add even more variety to the episodes, the shows will essentially switch locations. The crossover kicks off when Vandal Savage (Casper Crump), the main villain of Legends of Tomorrow, attacks Hawkgirl (Kendra Saunders), which forces Barry Allen to speed her off to Star City to place her under Team Arrow's protection.

"Most of the Flash episode takes place in Star City, and most of the Arrow episode takes place in Central City," Amell said. "We have a common villain, which was not the case last year. And, just in general, we've done an excellent job of weaving not just two shows, but three shows together."

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