The Big Cube (1969)

Renowned stage actress Adriana Roman, the muse of playwright Frederick Lansdale, is retiring to marry tycoon, Charles Winthrop. The marriage does not sit well with Charles' daughter, Lisa Winthrop, who dislikes her new stepmother if only because she is the other woman for her father's affections. However, on her father's urging, Lisa tries to get to know Adriana, to who she slowly warms. Meanwhile, Lisa attracts the attention of Johnny Allen, a womanizing, fortune hunting medical student who uses the school lab to produce and sell acid among the hip, mod crowd he hangs around. He romances naive Lisa who falls under his spell. After an incident with Charles, Johnny, sensing an opportunity to abscond with at least some of the Winthrop fortune by using Lisa's mistrust of Adriana, manipulates Lisa into trying to make Adriana go crazy, in large part through the lacing of her sedatives with acid. Adriana begins to hallucinate that Lisa and Johnny are trying to kill her, which is what they want her to believe through the hallucinations. In reality, Johnny is trying to kill her, of which Lisa is unaware. As Adriana tries to explain what she is going through to among others Frederick, he, who has always loved her himself, eventually believes that all is not that it appears on the surface. With new information at hand, Frederick, using the tools of his trade, tries to help Adriana through her troubled mental state.