Here Isaac let it drop, in true mathematician’s style, leaving the rest as an exercise for the reader. Daniel tried to communicate, with what he supposed were highly expressive shrugs, sighs, and brow-furrowings, that Isaac had quite lost him. But in the end the only thing for it was to swallow and say: "If Mr. Threader is so terrified of Jack’s being apprehended, why should he volunteer information as to the man’s habits?"