The Flash season 3 episode 17 titled Duet will feature a crossover with Supergirl. Kara (Melissa Benoist) will need the help of Barry (Grant Gustin) when Music Meister (played by fellow Glee alumni, Darren Criss) attacks.
Darren Criss played the character of Blaine Anderson in the Glee series. He worked with Benoist and Gustin, who played Marley Rose and Sebastian Smithe respectively. The three will have a reunion in episode 17, during a cross-over between The Flash and Supergirl.
Criss will play the role of Music Meister, the villain who has a silly face. In contrast, he possesses a dark and sinister characteristic. It will not be a full crossover since only a few things will be a part of Supergirl’s episode. Most of the story will take place in The Flash season 3 episode 17.
Despite Meister’s soft act, he has a darker motive behind his plans. His appearance will be a burden for Barry because of his problems with Savitar. Barry has to focus on another villain while Savitar continues to roam Central City. Presumably, the episode will let the audience enjoy the musical despite the unfortunate circumstances surrounding the two heroes.
In episode 16, Barry tried to save Wally (Keiynan Lonsdale) from the speed force. Barry managed to save Wally through the help of Jay Garrick (Jon Wesley Shipp). Barry and Wally managed to escape the speed force at the expense of Jay, who chose to remain in the speed force to let the other two speedsters. Barry and Wally will go back to the speed force to rescue Jay. Before they rescue Jay, they are confronted with a new problem, Supergirl is on comatose.
The Flash Season 3 Episode 17: Kara and Barry loses their powers
The official plot synopsis of episode 17 noted that Lar Mon-El (Chirs Wood) and Hank Henshaw (David Harewood) will arrive on Earth-1, carrying a comatose Kara, a.k.a. Supergirl. Team Flash will find out that the Music Meister attacked Kara and knocked her out. Mon-El and Henshaw could not wake her up and decided to turn to Team Flash to save her.
However, the Music Meister surprised Barry and puts him in a similar coma like Kara. Team Flash cannot cure Barry’s comatose state. Kara and Barry will wake up without their powers in an alternate reality. Their life in an alternate reality is like a musical. The only way to escape it is by following the script, as well as singing and dancing.