midnight
`` Sit up some night and watch , '' he advised the lad . `` Put the can in the usual place -- where do you keep it -- on the back step ? -- all right , put it there , and then hide back of the willow tree . You say it is done sometime between ten and twelve , for you go to bed at ten and your father comes home at midnight and finds the can empty ? That ought to make it easy for you , for you know when to watch for the thief . '' Jack 's father was engaged in some delicate electrical experiments that were conducted in his factory at night to escape the vibration caused by the heavy machines . Coming home from the Jordan office a little after then the next night after he had given Jack his advice , Doctor Hugh remembered what he had said and wondered if the boy had been successful in detecting the thief .