Murdock was the leader of the pickpockets in 1845 London.
He lived in a secret hideout that only he, Wilkins and Reg knew about. He provided shelter and food for Reg as long as the latter kept stealing watches for him.
After Jules and Verne escaped with their father, he and Wilkins pursued them to the Hog's Head tavern. Once there, Doc pushed a stack of barrels on top of them, incapacitating them until the police arrived and arrested them.