First, a key is a symbol of power and/or wealth

The speedy return of Bluebeard confirms that his trip was a ruse to give him the opportunity to test his wife's faithfulness. Bettelheim thinks that a sexual indiscretion has taken place in Bluebeard's absence (Bettelheim 1975). Undoubtedly the wife has disobeyed her husband, but the extent of her disobedience or betrayal is not apparent beyond the fact that she opened the door to the forbidden room. It is sure that Bluebeard counted on his wife's betrayal and set up the trap to quickly confirm it.

Bluebeard | Writing Through Media

Temptation is related to the curiosity and disobedience themes in the story. For some critics, the tale is a cautionary one against woman's innate wickedness that leads to the betrayal and ultimate destruction of her husband. This theme is once again present in the story of Pandora's box. It also alludes to the temptation story in the Garden of Eden in which Eve partakes of the forbidden fruit and thus gains knowledge forbidden by God the Father (Warner 1994). Christine Daae contends that the tale does not warn "against the moral consequences of sex, but of the practical consequences." In the days when childbearing was a principle cause of death, a husband essentially killed his wife by making her pregnant. In this way, Bluebeard is a story of everyday life (Daae 1998).

Bluebeard | The Book Review Page

Bettelheim addresses this aspect of the story in his interpretation of the tale. He considers Bluebeard's anger to be just since his wife betrays him, but the extreme nature of his anger is where Bluebeard's fault is found. He states: "The story tells that although a jealous husband may believe a wife deserves to be severely punished--even killed--for this, he is absolutely wrong in such thoughts" (Bettelheim 1975). This translation from Andrew Lang's The Blue Fairy Book reflects the Victorian attitude towards infidelity and the resulting anger. Zipes' modern translation uses: "My anger will exceed anything you have ever experienced" (Zipes 1989).