In late 1923 the newly married Daisy Dalrymple and Detective Chief Inspector Alec Fletcher of Scotland Yard take an ocean voyage to America for their honeymoon. Accompanied by Daisy's childhood friend Phillip Petrie, his wife, Gloria, and Gloria's father, American millionaire industrialist Caleb P. Arbuckle, Daisy and Alec are looking forward to a pleasant, uneventful trip. But at the last minute they are joined by Arbuckle's new friend, Yorkshire millionaire Jethro Gotobed, and his new wife, Wanda, a showgirl whom all but Gotobed are convinced is a gold digger of the worst sort.
Then, having barely lifted anchor, the ocean liner is beset by a series of suspicious accidents and deaths. With harsh weather and rough seas putting many-including Alec-out of commission due to seasickness, it soon falls to Daisy to figure out what connection there might be between the seemingly unrelated incidents. Convinced that there's a murderer aboard ship, Daisy must unmask the culprit or culprits before anyone else-especially herself-falls victim.