Five Dolls for an August Moon

A wealthy industrialist George Stark hosts a weekend gathering on his private island, bringing together scientists, couples, and a few hired staff including Professor Gerry Farrell, Jill, Trudy, Nick, Jack, Peggy, Marie, Charles, and Isabel. The scene hints at strained relationships and hidden agendas among the guests. The secluded setting foreshadows the coming confrontations and disappearances.

Farrell wakes to the realization that Stark and the others want him to sell his revolutionary resin formula. They offer him million-dollar cheques, hoping to press him into divulging the invention. Farrell insists he won't reveal the formula, claiming the original documents were secretly destroyed to protect it.

Jill discovers the dead body of Charles lying on the beach, signaling the first fatal consequence of the weekend's coercion. Stark has the body moved into a large walk-in freezer to hide it, while cutting off all contact with the mainland by sending the motor launch away and disabling the radio. The island's isolation becomes a weapon for the killers.

The following morning, Farrell is found dead on the beach after a gunshot, fueling fear and mistrust among the guests. Isabel, the Starks' teenage daughter, operates as the sniper and drags Farrell's body out to sea, signaling the start of the murderous spree. The group's veneer of civility quickly dissolves into chaos.

Peggy is shot dead while standing on the balcony, an unseen assailant leaving no immediate trace. The sudden violence escalates the fear among the survivors and complicates any chance of teamwork. The killer seems to have free rein within the island's confines.

Marie is found tied to a tree and stabbed in the chest, followed by Jill's discovery dead in her bathtub. Each corpse is placed into the freezer, keeping the deaths cloaked and heightening paranoia. The living begin to suspect one another as the supply of trust evaporates.

Stark, Jack, Nick, and Trudy hole up in Stark's living room for the night as tempers flare and distrust grows. Nick storms off in anger, leaving the others behind. The next morning, Nick's body is found cold and stored, signaling the killers' reach has extended.

Stark offers Trudy a cheque for Farrell's formula and reveals that the formula's microfilm still exists. He also uncovers a hidden motorboat that could take them to the mainland, intensifying the motive to coerce and escape. The plan to secure a fortune becomes all-consuming.

Jack confronts Stark and reveals he killed everyone to steal their cheques, including Peggy, in a bid to secure all the money. He shoots Stark dead during the confrontation, removing one competitor to wealth. The killer's plan begins to unravel as the body count rises.

In the eerie hush of the freezer area, Trudy and Jack attempt a handover, exchanging the formula for a cheque. They shoot each other; Trudy dies first, and Jack, dying, watches as Isabel seizes both the cheque and the formula. He tries to intervene but cannot stop her.

Some time later, Isabel, now wealthy, visits Farrell in prison and claims to love him. She explains that she drugged him with a sodium pentathol pellet to keep him unconscious, inadvertently triggering a confession about his partner's murder. Farrell, acknowledging his fate, provides her the account number to cash the remaining cheques, then she departs for Lausanne.