The Alias and Titanic alum will play Dr. Martin Stein, a brilliant but arrogant nuclear physicist who's sacrificed everything for his work in transmutation. After he discovers the particle accelerator fused him with the impulsive Ronnie Raymond (Amell), he makes it his mission to separate the two.
Garber will make his first appearance in Episode 12 and recur throughout the rest of the season.
As previously reported, Ronnie is a maintenance worker at S.T.A.R. Labs and Dr. Caitlin Snow's (Danielle Panabaker) fiancé. Amell will make his first Flash appearance in Episode 3.
What do you think of the Garber and Amell team-up?
The Flash airs Tuesdays at 8/7c.