Supergirl returns to Earth-1 on The Flash Season 3 Episode 17 "Duet."
But the girl of steel is in bad shape after tangling with a villain known as the Music Meister.
Team Flash is on the case, except it doesn't appear they have much luck in saving the superhero. Instead, Barry falls victim as well.
What happens when two superheroes are unconscious? A musical extravaganza!
Scroll through the photos and share your thoughts on the latest crossover.
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What now? - The Flash Season 3 Episode 17
A team full of scientists seems like the right place to bring Supergirl for help. But judging by the looks on everyone's faces, the solution will not be a simple one.
Alien Arrival - The Flash Season 3 Episode 17
Mon-el and Hank arrive from National City with an unconscious Supergirl. It's up to Team Flash to rescue their super friend from a musical villain.
What's going on? - The Flash Season 3 Episode 17
Team Flash is surprised by the unexpected arrival of their super friend.
Cisco's got questions - The Flash Season 3 Episode 17
Cisco seems a little suspicious about the alien arrival. Or maybe he's just wondering why Supergirl's unconscious and who the strangers are.
Cisco meets Mon-El - The Flash Season 3 Episode 17
Knowing Cisco, he's probably got a lot of questions for the prince. Mainly, what happened?!
Barry's down, too! - The Flash Season 3 Episode 17
Well, that didn't take long. Somehow the Music Meister managed to place Barry under the same spell as Kara. We can't blame Mon-El for looking worried.
Wait! There's more The Flash: Photos from "Duet"! Just click "Next" below: