The Big Cube

Adriana Roman, a successful stage actress, retires from the stage to marry Charles Winthrop, a wealthy tycoon. Lisa, Charles's daughter, instantly distrusts Adriana, viewing her as the 'other woman' who has won her father's affection.

Charles is killed in a boating accident, and Adriana suffers a concussion. The tragedy destabilizes Adriana and sets in motion the family tensions surrounding her marriage.

Lisa's new boyfriend, Johnny Allen, uses the tragedy to persuade Lisa that Charles was murdered. Adriana's threat to disinherit Lisa because of the will amplifies their conflict.

Johnny and Lisa conspire to lace Adriana's prescribed sedatives with LSD to drive her insane. Their plan aims to destabilize Adriana and influence the outcome of the will.

During a country drive, Adriana hallucinates that Johnny and Lisa are trying to throw her off a cliff. The episode marks a major break in her grip on reality.

Back at home, Adriana experiences further LSD-induced hallucinations as Johnny plays pre-recorded subliminal messages to push her over the edge. One message instructs her to leap from a window, deepening her peril.

Lisa saves Adriana from jumping, but the plot to depose Adriana continues. Adriana is committed to a mental hospital and declared legally insane, leaving her unable to carry out Charles's will.

In the aftermath, Adriana suffers amnesia and clings to the belief that Charles is alive. She remains unaware of Johnny and Lisa's scheming.

Johnny demonstrates his lack of genuine affection by seducing other women, including Lisa's friend Bibi. He then bribes Lisa to divorce him for $100,000 in exchange for her silence about what they did to Adriana.

Lisa decides to come clean about what she and Johnny did and confesses to Frederick Lansdale, a playwright friend of Adriana who has long loved her. He learns the truth and becomes involved in Adriana's recovery.

Frederick decides to write a play detailing Adriana's traumatic experiences and casts her in the lead role. He believes that replaying her experiences on stage could cure her and help her heal.

At the opening performance, Adriana starts to glimpse memories of the earlier events. She does not yet fully understand what those flashes mean, but they hint at the truth.

In the climactic third act, Frederick stages the actual recordings of Lisa and Johnny's voices. This revelation brings Adriana back to reality and makes Lisa confess on stage.

The play and Adriana's performance are a huge hit, and Adriana and Frederick are about to marry. Lisa reconciles with Adriana, while Johnny, shunned by his friends, begins an LSD-fueled spiral and is last seen on the floor.