Although his murdered friend was by all accounts a scoundrel a true "bounder" Edward Wales is determined to trap his killer by staging a seance using a famous medium. Many of the 13 seance participants had a reason and a means to kill, and one of them uses the cover of darkness to kill again. When someone close to the medium is suspected she turns detective, in the hope of uncovering the true murderer.

Marie St. Clair believes she has been jilted by her artist fiance Jean when he fails to meet her at the railway station. She goes off to Paris alone. A year later, mistress of wealthy Pierre Revel, she meets Jean again. Misinterpreting events she bounces back and forth between apparent security and true love.