Cassidy will reprise her role as Black Siren in the final two episodes of Arrow's fifth season and will continue playing Laurel's villainous doppelgänger as a series regular in Season 6.
"One of the things that most excites us about Arrow is that we go where the story takes us," executive producer Marc Guggenheim said in a statement. "Last year, the story took us to the tragic death of Laurel Lance. This year, our midseason finale reintroduced us to Laurel's doppelgänger, Black Siren. We were so taken by Katie's fearless interpretation of this character that we knew her story was not yet finished. We couldn't be more thrilled to welcome Katie back to Arrow as Black Siren, though as her appearances on Arrow and DC's Legends of Tomorrow this season show, she never really left the family."
Cassidy was a series regular on Arrow's first four seasons playing Laurel Lance, an attorney by day and the vigilante Black Canary by night, until her death at the hands of Damien Dahrk (Neal McDonogh) last April.
She made her first appearance as the Earth-2 metahuman Black Siren in The Flash's second season, when she clashed with Team Flash while working for the villain Zoom. Cassidy then returned in Arrow's most recent midseason premiere when Black Siren impersonated Earth-1 Laurel to mess with Oliver's head on Prometheus' (Josh Segarra) orders. Team Arrow ultimately defeated her and Black Siren has been in A.R.G.U.S. custody ever since.
Arrow airs Wednesday at 8/7c on the CW.
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