Again the tall old man reached the end of his beat nearest Terry, turned with military precision and went back. Terry slipped out and was instantly at the window again. All was as before. One of the guards had laid down his cards to light a cigarette, and dense clouds of smoke floated above his head. That partial obscurity annoyed Terry. It seemed as if the luck were playing directly against him. However, the smoke began to clear rapidly. When it had mounted almost beyond the strongest inner circle of the lantern light, it rose with a sudden impetus, as though drawn up by an electric fan. Terry wondered at it, and squinted toward the ceiling, but the ceiling was lost in shadow. He returned to his harborage between the two buildings for a fresh session of thought. And then his idea came to him. Only one thing could have sucked that straight upward so rapidly, and that was either a fan-- which was ridiculous--or else a draught of air passing through an opening in the ceiling. Unquestionably that was the case. Two windows, small as they were, would never serve adequately to ventilate the big single room of the bank. No doubt there was a skylight in the roof of the building and another aperture in the floor of the loft. At least that was the supposition upon which he must act, or else not act at all. He went back as he had come, passed the rear guard easily, and found Denver unmoved beside the heads Of the horses. "Denver," he said, "we've got to get to the roof of that bank, and the only way we can reach it is through the skylight." "Skylight?" echoed Denver. "Didn't know there was one." "There has to be," said Terry, with surety. "Can you force a door in one of those houses so we can get to the second story of one of 'em and drop to the roof?" "Force nothing," whispered Denver. "They don't know what locks on doors mean around here." And he was right. They circled in a broad detour and slipped onto the back porch of the blue house; the guard at the rear of the bank was whistling softly as he walked. "Instead of watchdogs they keep doors with rusty hinges," said Denver as he turned the knob, and the door gave an inch inward. "And I dunno which is worst. But watch this, bo!" And he began to push the door slowly inward. There was never a slackening or an increase in the speed with which his hand travelled. It took him a full five minutes to open the door a foot and a half. They slipped inside, but Denver called Terry back as the latter began to feel his way across the kitchen. "Wait till I close this door." "But why?" whispered Terry. "Might make a draught--might wake up one of these birds. And there you are. That's the one rule of politeness for a burglar, Terry. Close the doors after you!"