Anna Barlow is a Police Detective and a trained expert in undercover work. She is investigating the disappearance of three women with a connection: they all worked as escorts. In the course of the investigation, Anna is able to locate the area where the last woman went missing. She sets up an identity that is similar to that of the missing women on the website of an escort agency. She receives a request from a man who calls himself Bluebeard. Anna accepts the job and is sent instructions for being picked up by car. She is driven to an underground location in a wealthy neighbourhood. Bluebeard receives her. He adresses her as Judith.
Bluebeard asks Judith several times if she wishes to follow him inside the place he calls his castle or would prefer to turn back and return home. Judith insists that she will never turn back.
Judith studies the interior of the building. It is cold and dark; the walls are wet. When he asks why she followed him, she explains her intent to bring light, air and warmth to the place.
Judith sees that there are seven rooms and instructs Bluebeard to open up their doors. Bluebeard refuses, reminding Judith of the rumours about him. Judith demands the key to the first door. When she tells Bluebeard that she loves him, he gives it to her. When Judith is about to open the door, she hears a crying sound. Judith assumes the walls are groaning.
Judith opens the first door and describes the items in the room: Hooks, knifes. She notices blood on the walls. This is his torture chamber, Bluebeard explains. Judith requests the other keys. Bluebeard asks why and she explains once again that she loves him. He hands her the second key.
In the next room Judith finds weapons. This is the armoury, explains Bluebeard. Here too: dried blood on all the weapons. Judith then asks for the third key, becoming insistent, despite Bluebeard‘s warnings. She says that she loves and now belongs to him. He must now show her the whole castle and open all the doors. Bluebeards tells Judith that he will give her three more keys but that she may not ask any questions.
Behind the third door lie immeasurable treasures and gold jewellery. The treasure chamber. Judith appears impressed, then gasps in shock: here too, everything is covered in blood.
Bluebeard now urges Judith to open the fourth door. She does so and finds Bluebeard’s secret garden behind it. A wonderful place, but Judith once again shrinks back in horror. The garden is soaked with blood. She asks who watered the garden, but Bluebeard avoids the question, pointing out instead that the castle truly is becoming brighter because of her presence. He urges Judith to open the fifth door.
The fifth room is where Bluebeard surveys his domain. Now it all belongs to Judith, Bluebeard tells her. He praises her for bringing in light, but she sees clouds which cast bloody shadows. She reminds him that there are still two doors which remain to be opened.
Bluebeard praises Judith once again and asks her to kiss him. But she says she will not tolerate any closed doors. She instructs Bluebeard to open the final two doors, come what may. Bluebeard is reluctant, but finally gives Judith one more key.
He follows her into the next room. When she asks about the water she sees there, Bluebeard says that these are tears.
Judith begins to ask Bluebeard about his former wives. Bluebeard begs her to love him and desist from further questioning, but she insists, asserting that all the blood must point to the truth behind the circulating rumours. Behind the final door Bluebeard’s former wifes must lie murdered in their own blood. She demands the seventh key which Bluebeard hands to her.
Behind the seventh door, Judith indeed finds Bluebeard’s former wifes – alive. According to Bluebeard, each of the three women stands for a time of the day: morning, afternoon and evening. Judith is supposed to join them, representing the night.
Although Bluebeard exposes Anna’s true identity while they make their way through the underground building, she manages to take his gun from him and achieve the aim of her journey: To free the three women the man has abducted.