A young couple, Guy and Margaret, buy a rundown yacht, the Cyclops, with the intention of renovating it as their home-on-the-sea. However, they soon realize that the ship is actually haunted by the ghost of its former owner, Professor Martineau, who was murdered on board along with his lover and engineer. As the couple tries to uncover the truth behind the haunting, they must navigate a web of deceit and danger that threatens to destroy their relationship and their lives.