Curse of the Crimson Altar is a 1968 British horror film directed by Vernon Sewell and starring Christopher Lee, Boris Karloff, Barbara Steele and Mark Eden. The film was produced by Louis M. Heyward for Tigon British Film Productions. The film was edited and released as The Crimson Cult in the United States. The screenplay, by Doctor Who writers Mervyn Haisman and Henry Lincoln, was based (uncredited) on the short story "The Dreams in the Witch House" by H. P. Lovecraft. This film also featured the final British film appearance of horror icon Karloff.The film opened in England in December 1968, then later premiered in Los Angeles on April 15, 1970 on a double bill with Horror House starring Frankie Avalon. It later went into general release across the United States on Nov. 11, 1970, on a double bill with Count Yorga, Vampire.