The CW Television Network has released an official synopsis for the highly-anticipated musical crossover episode of The Flash. The star-studded occasion will air on Tuesday, March 21st, and will feature characters from both The Flash and Supergirl.

With last year's crossover episode between the two shows primarly existing on Supergirl, this episode appears to be the reverse, with Hank Henshaw and Mon-El traveling over to Earth-1 in need of the team's help with saving Kara.

It has been reported that the cast members who will sing in the musical are Grant Gustin (Barry Allen/The Flash), Jesse L. Martin (Detective Joe West), and Carlos Valdes (Cisco Ramon/Vibe), as well as Melissa Benoist (Kara Danvers/Supergirl), Jeremy Jordan (Winn Schott), Arrow and Legends of Tomorrow's John Barrowman (Malcolm Merlyn) and Legends' Victor Garber (Martin Stein). Songs from the episode will be penned by fellow CW star Rachel Bloom, as well as the recent Oscar-winning duo of La La Land. Check out the synopsis below:

DARREN CRISS (“GLEE”) GUEST STARS AS THE MUSIC MEISTER IN THE FLASH AND SUPERGIRL MUSICAL CROSSOVER – Barry (Grant Gustin) and team are surprised when Mon-El (guest star Chris Wood) and Hank Henshaw (guest star David Harewood) arrive on their Earth carrying a comatose Supergirl (guest star Melissa Benoist) who was whammied by the Music Meister (guest star Darren Criss). Unable to wake her up, they turn to Team Flash to save her. However, the Music Meister surprises The Flash and puts him in a similar coma, one that Team Flash can’t cure. Kara and Barry wake up without their powers in an alternate reality where life is like a musical and the only way to escape is by following the script, complete with singing and dancing, to the end.

Based on the characters from DC, The Flash is from by Bonanza Productions Inc. in association with Berlanti Productions and Warner Bros. Television, with executive producers Greg Berlanti (Arrow, Supergirl), Andrew Kreisberg (Arrow, The Flash), Sarah Schechter (Arrow, DC’s Legends of Tomorrow) and Aaron and Todd Helbing.