The CW has released the official synopsis for "Invincible," the upcoming May 17 episode of The Flash, which guest-stars Arrow's Katie Cassidy as Black Canary's Earth-2 counterpart, Black Siren.
Jesse Warn directed the episode with story by Greg Berlanti & Andrew Kreisberg and teleplay by Brooke Roberts & David Kob.
The synopsis also says that Wally West will "take to the streets" to help The Flash, seemingly suggesting that our speculation about him getting powers in the next couple of episodes might be on point.
After Zoom (guest star Teddy Sears) unleashes an army of Earth-2 meta-humans on Central City, Barry (Grant Gustin) is shaken when he sees their leader is the Black Canary’s Earth-2 doppelganger, the Black Siren (guest star Katie Cassidy). Meanwhile, Wally (Keiynan Lonsdale) takes to the streets to help The Flash stop the meta-humans, which worries Joe (Jesse L. Martin). Iris (Candice Patton) and Henry (guest star John Wesley Shipp) are concerned about Barry taking on Zoom.