Goodbye Gemini is a 1970 British psychological horror film directed by Alan Gibson and starring Judy Geeson, Martin Potter, Michael Redgrave, and Alexis Kanner. Based on the novel Ask Agamemnon by Jenni Hall, it concerns a pair of unusually close fraternal twins, Jacki and Julian, discovering Swinging London while home on Spring Break. Their experiences complicate the pair's relationship, which is already strained due to Julian's incestuous fascination with his sister, which he sees as a natural manifestation of what he believes to be the pair's hive-minded nature.