The Lone Wolf by Louis Joseph Vance

Though it had been nearly eight when they entered the restaurant, it was something after eleven before Lanyard called for his bill.

"We've plenty of time," he had explained; "it'll be midnight before we can move. The gentle art of housebreaking has its technique, you know, its professional ethics: we can't well violate the privacy of Madame Omber's strongbox before the caretakers on the premises are sound asleep. It isn't done, you know, it isn't class, to go burglarizing when decent, law-abiding folk are wide-awake. Meantime we're better off here than trapezing the streets."