Number Two (the name preferred by her over her given name, Pencilla) is Mr. Benedict's first adopted daughter. She passed his tests wonderfully, but there were no other children to pass that year, and Mr. Benedict needed a team of children. He thought her talents so useful, though, that he hired her on as an assistant.
Number Two has insomnia, and therefore needs to eat almost constantly. If she fails to consume enough food, she tends to get nervous and irritable. Her sleeplessness proves very useful on more than one occasion. however. For example, she manages to get a tremendous amount of work done on the eve of the Society's trip to the Institute, and in The Perilous Journey, her restlessness allows her to get the pin in her cuffs unlocked, and thus allowing her to escape. Her real name was not revealed until the end of The Prisoner's Dilemma, in which Constance tricked her into thinking it, and thus plucking it from her mind.
- Both of her names, Number Two and Pencilla, are a reference to her appearance, which is rather like a pencil.