When Slick, a pickpocket, hears that Carmina is to marry Albert Johnson, the detective, be swears to be avenged upon him. One day Johnson is followed by Slick, who plunges a stiletto into his back and leaves him dead on the ground. Carmina, who feels sure that Slick is guilty, fails to prove her case in court as Slick brings forward a strong alibi. She determines to take the investigation into her own hands and goes, disguised as a maid, to work at the house where Slick boards. It is not long before she discovers that Slick has a strange fear of blood stains and that he is much worried because of a stain on a coat sleeve. Slick removes the stain by means of acid, but Carmina, who finds this out, stains his sleeve again with red ink. When Slick sees the stain he is terrified, and begins to think that he is haunted. First in one place and then in another, Carmina smears the red ink, on the table-cloth under his plate, on his towel and on other clothes. One night, Carmina pours a stream of red ink over Slick’s pillow, awakening him. In the moonlight he sees the spreading stain and then sees a ghostly hand reaching in the window, holding a stiletto, apparently dripping with blood. Crazy with fear, he rushes shrieking from the room and meets Carmina, who discloses herself to him. Confronted again by the bloodstained coat, he confesses to the crime and begs for mercy. Carmina sneers at him and hotly denounces him, handing him at once over to the police. When he finds himself arrested and compelled to face the consequences of his deed, his mind gives way and he is carried off. a violent lunatic. Carmina has succeeded; her husband is avenged.