At a masked ball Philip Greycourt, a wealthy society man who has tired of his easy conquests of women, becomes interested in a grey-gowned woman who will not remove her mask. Later invited with his friend, Frank Sturtevant, to visit the country home of the Villiers, he finds in Helene Villiers, the second wife of his host, his lady of the mask. Catherine, the step daughter, falls in love with Philip, but he is so infatuated with the mother that he does not notice it. Helene enjoys a flirtation with Philip and leads him on until finally she invites him into her sitting room, during the absence of her husband. Losing control of himself, Philip clasps Helene in his arms, and the returning husband sees the shadow on the curtain. Warned by the maid, Philip runs into the hall and entering the first door, finds himself in Catherine's bedroom. Mr. Villiers finds him there and Philip says he and Catherine are to be married the next day. After the wedding, Catherine is perfectly happy, not knowing of the attachment between her stepmother and Philip, but Helene tries to still carry on their flirtation and, becoming jealous of Catherine, tells her all. Believing Philip still loves Helene, Catherine leaves a note for him and takes passage on a steamer. Philip, however, has grown to love her and throwing Helene aside forever, he boards the boat and sails away with Catherine. - Moving Picture World, July 7, 1917
Release date listed as 1917 in AFI Index.