The name of the man who betrayed the ten Booms was Jan Vogel.
Jan Vogel worked with the Gestapo, exposing members of the Resistance to them. He was responsible for sending a great many individuals to prison and worse; he had aided the Gestapo from the first day of the occupation of Holland, having operated in Ermelo before coming to Haarlem. On the day of the raid at the Beje, Vogel had come to the establishment and insisted on speaking with Corrie, who was ill. When Corrie came down from her sickbed to meet him, he told her that his wife had just been arrested because they had been hiding Jews, and asked for money with which he would be able to bribe a policeman to be lenient with her, or perhaps let her go. Corrie sensed that something was not right with the "small sandy-haired man;" there was something suspicious in his demeanor, in the way "his eyes seemed to make a circle around (her) face," and yet, she did not want to risk being wrong. She told the man she would get the money and that he should "come back in half an hour." Shortly thereafter, the Beje was raided and Corrie and her family were arrested.
Corrie and Betsie are incarcerated at Vught when they learned the identity of their betrayer. Corrie, thinking about how Vogel had caused the death of her father and no end of suffering to the rest of her family, was filled with rage, but Betsie reacted with forgiveness, and actual sympathy for a man who must be so miserable with so much on his conscience. Guided by the boundless love of her sister, Corrie prayed to be forgiven for her bitterness towards her betrayer, and was blessed with a deep sense of acceptance and peace (Chapters 9 and 12).