Months after adding Robbie Amell as Ronnie Raymond, The Flash has cast Victor Garber as Martin Stein, the other half of the villainous Firestorm. We also have new photos from the set that confirm Reverse-Flash's presence in the show, but there will be spoilers if you haven't watched this week's series premiere, so read on at your own risk.

Victor Garber will show up in The Flash's 12th episode, the first appearance in a major recurring arc. Dr. Stein is described as a "brilliant but arrogant nuclear physicist who has sacrificed everything, including a marriage, for his work in transmutation." He discovers that the particle accelerator has fused him together with the younger, more impulsive Ronnie Raymond, as he races to find a way to separate them both before time runs out.

The Martin Stein and Firestorm characters have appeared on several animated properties before, such as Super Friends and Justice League: Crisis on Two Earths but this will be the first live-action appearance.

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Victor Garber joins a growing cast of DC Comics characters including Dominic Purcell (Heat Wave), Wentworth Miller (Captain Cold), Clancy Brown (General Wade Elling), Robert Knepper (The Clock King) and Kelly Frye (Plastique).

We reported yesterday that The Flash series premiere drew in 4.5 million viewers on Tuesday night, the largest series premiere for The CW since The Vampire Diaries debuted in 2009.

Victor Garber currently has recurring roles on Showtime's Web Therapy and Starz's Power.

In related news, this week's series premiere of The Flash teased several surprising plot developments, including the title character's arch nemesis "Reverse-Flash," who is believed to be the man responsible for the murder of Barry's parents. Today we have confirmation that The Flash and Reverse Flash will indeed square off at some point in the series, with new photos from the set showcasing a battle between these two characters. Take a look at the images below, then read on for more information.

Of course, we don't know exactly who will play Reverse-Flash yet, since it appears to be a stunt double wearing the yellow and black suit in the images, but The Flash premiere did offer a few hints. The name of Rick Cosnett's character, Detective Eddie Thawne, is clearly inspired by Reverse Flash's real name in the comic books, Eobard Thawne. In the comics, Eobard is a super-fan of Barry Allen from the 25th Century, who travels back in time to present day.

There is also speculation that Tom Cavanagh's Harrison Wells, a character who does not appear in the DC Comics, may be Reverse Flash as well. The final scene of the series premiere showed Harrison standing up from his wheelchair for the first time, and entering a secret room where he looks at a newspaper from 10 years into the future, which shows the disappearance of The Flash. Executive producer Andrew Kreisberg teased yesterday that time travel will be an important factor in the show, but it still remains to be seen who exactly will be Reverse Flash. Thanks to the photos above, though, we know for a fact that his presence will be felt at some point in the future of The CW series.