A crossover episode with "Supergirl" will conclude in "The Flash" Season 3 episode 17 titled "Duet." Barry Allen/The Flash (Grant Gustin) and his team will be surprised to see Mon-El and Hank Henshaw carrying a comatose Supergirl when they arrive on their Earth.
Supergirl was whammied by the Music Meister (Darren Criss). Mon-El (Chris Wood) and Hank Henshaw (David Harewood) cannot wake her up so they turn to Team Flash to rescue her.
However, the Music Meister will surprise The Flash. The former will put the latter in a coma like what he did Supergirl.
When Kara and Barry wake up, they do not have their powers. The two are in an alternate reality where life is like a musical and following the script is the only way to escape.
Whether or not Kara and Barry will perform a duet in "Duet" to fight the Music Meister has yet to be seen. The episode will also feature Candice Patton as Iris West, Danielle Panabaker as Caitlin Snow, Carlos Valdes as Cisco Ramon, Keiynan Lonsdale as Wally West, Tom Cavanagh as H.R. Wells, Jesse L. Martin as Joe West, John Barrowman as Malcolm Merlyn, Victor Garber as Martin Stein and Jeremy Jordan as Winn Schott.
"The Flash" Season 3 episode 17 titled "Duet" will air on The CW on March 21, Tuesday, at 8:00 p.m. Watch the trailer here: