To keep a secret watch on a house in a city street is a feat requiring no little skill. Though French had reached the stage in which he left most of such work to his underlings, he was a past master in the art. Yet as first seven, then eight, then nine struck from the surrounding clocks it required all his ingenuity to give the appearance of being detained on some ordinary and unimportant business. He strolled up and down, hiding in alley ways and behind projecting corners and moving on at intervals from one such place of vantage to another. He had engaged a taxi in case his quarry should do the same, and for a good part of the time he employed the old device of sitting back in its deepest recesses while the driver gave a lengthy first aid to his refractory engine. At last, when he had become stiff with cold and was cursing mentally but steadily at the delay, Pyke appeared and started off quickly towards Russell Square. French drew back into the entry in which he was taking cover and allowed him to pass, then having signed to his driver to keep him in sight, he followed the quarry as closely as he dared. Pyke turned down Montague Street, walking by New Oxford Street and Charing Cross Road to Charing Cross Station. He seemed about to enter the station, but, suddenly glancing round, he turned to the right and dived down the steps to the Hampstead and Highgate tube. French had already settled up with his driver and he followed without delay. Keeping close behind, French shadowed his man to the platform and entered the next coach of the Hampstead train which the other boarded. At each station he watched the alighting passengers, but it was not until Hampstead was reached that Pyke appeared. Twenty feet apart, the two men passed out into the street and up the hill towards the Heath. At the wide space at the entrance to the Heath French fell further behind. Pyke was now strolling easily along, as if out for a breath of air before bed. He passed in towards the left near Jack Straw’s Castle, taking one of the side paths which led to the wilder areas. Here were fewer people, and French dropped back till he could just see the man’s light fawn coat like a faint smudge against the dark background of the trees.