That there had been a development in the room raided which had disturbed for the moment even the steady poise of the great detective, none knew but himself.
In T. Burton Potter he had recognized one of the men he most wanted to get hold of just now. The other was Andrew Lampton, but he felt that he could let the hunt for Lampton go for the present, until he had his hands on the elegant Potter.
What was Potter doing while Nick laughed at the cleverness of his escape from the room? Well, he was trying to achieve a get-away under extremely difficult circumstances.
Once clear of the room where he had managed to give the detective the slip, he made a half turn toward the downward flight of stairs. But another officer showed himself at the bottom. So he swung around and dashed up the stairs to the floor above.
In the darkness, Nick was not sure whether his man had gone up or down. This involved another loss of a few moments. But his keen ear soon told him where Potter was, and up the stairs he went after his man.
T. Burton Potter heard his pursuer, and he did not dodge into any more rooms. Instead, he continued up the stairs, flight after flight, with one last, desperate hope in his heart—just one! That was that he might escape by way of the roof.
He had one advantage over Nick, in that he knew the house well, while this was the first visit of the detective.
Aided by this fact, and by the darkness, with many twists and turns at landings and on the stairs themselves, T. Burton Potter was in the garret at about thirty seconds ahead of Nick.
He lost half that gain in unbolting a trapdoor and forcing it open, so that he could crawl through to the roof. It was a serious loss to him, for the detective almost had him by the legs as he clambered through. Before he could slam down the trap door, Nick was out on the roof after him.
It is not an uncommon thing for detectives and uniformed police officers to chase crooks over roofs. Some thrilling experiences of this kind could be related by a great many policemen, but each story of the pursuit of some desperado over the roofs of skyscrapers has features of its own that make it stand out from all others.