The first episode of The CW's upcoming "Crisis on Infinite Earths" event will deliver the superhero team-up viewers have been been expecting.

The CW has released the storyline synopsis for the crossover's opening chapter in Supergirl. Appropriately titled "Crisis on Infinite Earths: Part One," the episode brings Supergirl together with The Flash, Green Arrow, Batwoman, White Canary, The Atom and Superman. The event has long promised to join together the Arrowverse heroes, and has also announced cameos from other DC characters outside the Arrowverse.

The official synopsis reads as follows:

THE KICKOFF TO THE EPIC TELEVISION CROSSOVER EVENT, CRISIS ON INFINITE

EARTHS - The Monitor (guest star LaMonica Garrett) sends Harbinger (guest star Audrey Marie Anderson) to gather the worlds’ greatest heroes - Supergirl (Melissa Benoist), The Flash (guest star Grant Gustin), Green Arrow (guest star Stephen Amell), Batwoman (guest star Ruby Rose), White Canary (guest star Caity Lotz), The Atom (guest star Brandon Routh) and Superman (guest star Tyler Hoechlin) - in preparation for the impending Crisis. With their worlds in imminent danger, the superheroes suit up for battle while J’onn (David Harewood) and Alex (Chyler Leigh) recruit Lena (Katie McGrath) to help them find a way to save the people of Earth-38. Jesse Warn directed the episode with story by Robert Rovner & Marc Guggenheim and teleplay by Derek Simon & Jay Faerber (#509). Original airdate 12/8/2019.

"Crisis on Infinite Earths" begins Sunday, Dec. 8 on Supergirl, then continues in Batwoman on Monday, Dec. 9, and then picks up in The Flash on Tuesday, Dec. 10. After a winter hiatus, the crossover concludes on Tuesday, Jan. 14 on both Arrow and DC's Legends of Tomorrow.