Arthur Askey plays meteorologist Arthur Pilbeam who is jilted by his fiancée Betty because he has to speed back to the BBC every hour, on the hour due to his internationally vital job of creating the BBC pips. As he cannot be fired during wartime and wanting to avoid all women, he is assigned the solitary job of sending weather reports from a remote Scottishlighthouse. Before taking a boat from the mainland during the four hours of daylight that are available for the time of year, the locals warn him he will go mad from isolation and the curse of a mermaid within a month as others have.
Authur Pilbeam soon has his peace shattered as a stowaway is found in the lighthouse and the survivors of a torpedoed ship arrive. Things are crowded on the lighthouse until one-by-one people start to mysteriously disappear, leaving Pilbeam to discover what has been happening to everyone and why.