As the saying goes, when one door closes, another opens. Following his reoccurring role as Ken Cosgrove on Mad Men, Aaron Staton will appear in a reoccurring role on Showtime’s Ray Donovan Season 3. According to Deadline Hollywood, Staton, who has also appeared in bit parts on The Good Wife and Person of Interest as well, will play Mr. Donellen, “a strict yet kind high school teacher with a tragedy in his past.” Little else is known about how Donellen will figure into the world of Liev Schreiber’s titular L.A. fixer, especially considering how things were left with Mickey (Jon Voight), the rest of Donovan’s friends and family, and the FBI at the end of season 2.

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Image via Showtime

The casting of Staton is only the latest in a long line of casting news for the Showtime series. Earlier this year, Fairuza Balk (Almost Famous) joined the cast along with Shree Crooks, and Katie Holmes has been confirmed as well, playing a businesswoman who must enlist Donovan’s services at the behest of her studio-head father. Her father will be played by another new name to the Ray Donovan Season 3 cast: the great Ian McShane. As for Staton, it’s unknown exactly how much his half-blind, science-fiction-writing character will appear on Mad Men in its final episodes leading to the series finale. Meanwhile, Schreiber has been keeping mighty busy outside of the Showtime series, with major roles in the science-fiction drama The 5th Wave and Thomas McCarthy’s upcoming Spotlight, about the Boston Globe’s hand in revealing rampant cases of child molestation in the Massachusetts Catholic Archdiocese.

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Image via Showtime