One half of a murder-mystery writing team kills his more talented partner after the latter announces his intentions to go solo which would ultimately leave the former in financial ruin. Later a grocery store owner, who has important information pertaining to the case and has romantic desires for the killer, sees this incident as an opportunity to blackmail him into having a relationship with her. Feeling cornered, he kills her and tries to make it look like she'd fallen off a boat and drowned in a drunken stupor.