A notorious international lady criminal, Mrs Valentine Kempel, has taken an apartment in the centre of the city, decorating it with mad luxury. From her nest she spreads her web of intrigue over the city and woe the poor victims caught in it. She got her nickname, "The Predator Spider," for a reason. Her latest victim is a young artist, Charlie Falkenberg, who is as naïve and romantic as a child. Using her feminine wiles, she turns the young man’s head around so completely that he is prepared to die for her.
To trick him into committing a crime, she pressures Charlie to forge his wealthy merchant brother’s signature on a bill of exchange, but Charlie refuses and chooses death by his own hand rather than the shame of facing the Predator Spider again. Vowing to avenge his brother’s death, the merchant Falkenberg hires a detective, Asbjørn Krag. Hearing about this from her network of spies, the Predator Spider plans to smear the merchant Falkenberg as a card sharp, but her plot is foiled thanks to the nimble wits of detective Krag.
Unfazed, the Predator Spider ups the stakes, luring Falkenberg’s fiancée into her clutches. Meanwhile, detective Krag manages to set up a meeting with the Predator Spider at the Grand. Getting Falkenberg’s fiancée back proves to be a tough job, but he gets help from a man trying to escape from the Predator Spider’s web. Krag gains access to the lady criminal’s home, where he throws off his disguise and forces the abductress to reveal where she is hiding Falkenberg’s fiancée. Krag stumbles when the Predator Spider presses a secret button, alerting her henchmen, but soon the web she has used to trap her victims collapses on her.