Barty Crouch Jr.'s mother knew she did not have much time left. When she visited her son in Azkaban, she used Polyjuice Potion to exchange identities with him.
She was the one who died in Azkaban, while Barty Crouch Jr. was hidden at home by Barty Crouch. For thirteen years, he had been controlled by the Imperius Curse, wearing an Invisibility Cloak from morning to night.
The Crouch family's House-elf, Winky, was responsible for watching him, but no matter how flawlessly Barty Crouch covered his tracks, someone still found out.
That person was Bertha Jorkins. She had come with documents for her superior, Barty Crouch, to sign, but he happened to be away from home.
Hearing Barty Crouch Jr. and Winky talking, she came over to investigate and guessed that Barty Crouch Jr. was beneath the Invisibility Cloak.
When Barty Crouch returned home, Jorkins confronted him face-to-face, and he cast an extremely powerful Memory Charm on her.
Because the spell was too powerful, it caused permanent damage to Jorkins's memories.
Perhaps Barty Crouch had done it to keep a promise to his wife, perhaps for his future at the Ministry of Magic, or perhaps for his son. But whatever his reason, he had indeed harmed an innocent person.
The next part of the story began during last summer's break.
Ludo Bagman, the notorious gambling addict of the British Wizarding World, had planned to make a fortune through the Quidditch World Cup.
As head of the Department of Magical Games and Sports, he was fully responsible for the World Cup's global broadcasts.
To keep Jorkins from ruining things, he had deliberately approved a long leave for her. As a result, Jorkins, who had gone to visit relatives in Albania, was found by Voldemort, who learned that Barty Crouch Jr. was still