Barry Allen and Kara Zor-El’s showdown against the Music Meister will begin in Supergirl: Season 2, episode 16, airing March 20th, and will continue onto the March 21st episode of The Flash, which is Season 3, episode 17. Like with the last big Arrowverse crossover , this team-up will kick off at the end of Supergirl and the bulk of it will take place on The Flash. The Flash episode is called “Duet” and will be directed by Dermott Downs.