Down on his luck architect and builder Edward Shaw (Keith Andes) is approached by Mrs Doris Hillman (Angela Lansbury) with a business proposal: buying land together, on which he would build houses that she would then sell, using her experience as a former real estate broker. Her husband, a wealthy businessman, would be willing to contribute half a million dollars as capital for the venture. Mrs Hillman also seems interested in more than a purely professional relationship. Shaw starts an affair with her and accepts the business offer. However, an accidental discovery leaves him convinced that the Hillmans' interest lies less in the long-term profits of the venture than in the $175,000 key man insurance policy he took on himself as a precondition for the deal, and that an attempt on his life is imminent.