Mad Men alum Rich Sommer has been cast in a lead role opposite Perry Mattfeld on the new CW midseason drama series In the Darkfrom CBS TV Studios and Ben Stiller’s Red Hour Films. He will play Dean, replacing Austin Nichols, who played the role in the pilot.

Written by Corinne Kingsbury and directed by Michael Showalter, In the Dark centers on Murphy (Mattfeld), a flawed and irreverent woman who just happens to be blind and is the only “witness” to the murder of her drug-dealing friend, Tyson. When the police dismiss her story, she sets out with her dog, Pretzel, to find the killer while also managing her colorful dating life and the job she hates at Breaking Blind — the guide-dog school owned by her overprotective parents.

Sommer’s Dean is a salt-of-the-earth cop. He’s called in to investigate when Murphy claims she has discovered Tyson’s dead body in an alley. He’s put on the case because he has a blind daughter, and it’s thought that he may be sensitive to Murphy’s situation. He also initially thinks that Murphy’s claim was the result of a drunken delusion. But as Murphy cleans up her act and presses the police to investigate, Dean begins to lend credence to her claims.

Brooke Markham and Keston John co-star.

Sommer co-starred on Mad Men as Harry Crane for the acclaimed series’s seven-season run on AMC, sharing in the cast’s two drama ensemble SAG Awards. He is currently recurring on the Netflix comedy series GLOW. Sommer is repped by Domain Talent and Harris Spylios of Davis Spylios Management.