Hammer was originally cast as former White House counsel John Dean in the upcoming Starz series, but was forced to withdraw from the project amid sexual abuse allegations earlier this year, and Deadline reports Stevens is now set to take on the role.
Gaslit is based on the Slate podcast series Slow Burn, which focuses on the untold stories and forgotten characters of the Watergate scandal, which ended Richard Nixon’s U.S. presidency in the 1970s.
Roberts will play Martha Mitchell, the Arkansas socialite who was one of the first people to blow the whistle on Nixon’s involvement with Watergate, while Penn is attached to star as John Mitchell, Nixon’s loyal close friend and the Attorney General.
Roberts is among the executive producers, alongside director Matt Ross.
Stevens was most recently seen in the German film I Am Your Man, as well as Blithe Spirit.
He is also attached to new Amazon series Solos, joining a star-studded cast that includes Morgan Freeman, Anne Hathaway, Helen Mirren, Anthony Mackie, Uzo Aduba and Constance Wu.