Mariclare Costello, an actress who had worked as a casting director on Hancock's stage production of "The Freaking Out of Stephanie Blake" (1967), was cast opposite Lampert as the mysterious hippie, Emily. Hancock was specifically taken by Costello's physical features, which included bright red hair and a pale complexion, which he felt was befitting of the vampiric Emily. Barton Heyman and Kevin O'Connor were given the roles of Jessica's husband Duncan, and the couple's friend Woody, respectively; Hancock had worked with Heyman and O'Connor previously, as they had appeared in his 1967–1968 stage production of "A Midsummer Night's Dream". Heyman had been Hancock's first choice in the role of Duncan. Alan Mason, who portrayed the doomed antique dealer Sam Dorker, had also acted in several of Hancock's plays. Gretchen Corbett, also an established New York-based stage actress from Portland, Oregon, was cast as the mysterious mute girl whom Jessica encounters, and was the only performer in the principal cast to have not worked with Hancock prior.