Theodore is asked to talk to some villain from Voldemort's people. They caught one of the death eaters but since Theo is a scary and manipulative person they choose him to talk to this death eater. When he entered the dungeon someonewas facing the wall and he couldn't see who, when Theo called them, when the person turned around it was...you.

"Little sister?" He asked in disbelief. He wanted to cry but he wants to know if this was a joke or what.