She had told Darzac that if her father should know of her dishonour, she would kill herself.

Monsieur Darzac had sworn to silence her persecutor, even if he had to kill him.

He was outwitted and would have succumbed had it not been for the genius of Rouletabille.
Mademoiselle Stangerson was herself helpless in the hands of such a villain.

She had tried to kill him when he had first threatened and then attacked her in The Yellow Room.

She had, unfortunately, failed, and felt herself condemned to be for ever at the mercy of this unscrupulous wretch who was continually demanding her presence at clandestine interviews.