The Arrow actress will play Laurel Lance’s Earth-2 doppelganger, Black Siren

We’ve known for a while now that (former) Arrow star Katie Cassidy would be guest-starring on The Flash later this season. Producers revealed weeks ago that she would appear in an upcoming episode as Black Siren, the Earth-2 version of Laurel Lance. Now we have first details on the episode!

Related: Synopsis Released for Kevin Smith’s Flash episode, ‘The Runaway Dinosaur’

Airing on Tuesday, May 17, “Invincible” will see Zoom bringing an army to help stop The Flash. Here’s the newly released synopsis:

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.

It’ll be nice to see Cassidy back on the screen after Laurel’s unfortunate demise on Arrow, even if it is just an Earth-2 doppelganger.

On this week’s “Rupture,” Barry’s quest to regain his powers will put Joe and Henry at odds, while the brother of Cisco’s Earth-2 doppelganger comes to Central City looking for revenge. Next week, we get the highly-anticipated Kevin Smith episode, 4×21 – “The Runaway Dinosaur.”

Arrowverse Crossover: "Crisis on Earth X"

Related: Poster, Trailer, & Stills From The Flash 2×20 – ‘Rupture’

We’ll have all the details on The Flash‘s final Season Four episodes as they’re announced, so be sure to follow us on Twitter, Tumblr, and Facebook for all the latest!