They saw him buying a ticket at the station and also purchase a late edition of the evening paper. Then he descended to the platform of the tube and took a train going towards Piccadilly.
Gerald and Marigold, who had separated, travelled on the same train until, on arrival at Knightsbridge, the man they were watching alighted. Marigold, who had been on the alert at each station, saw him emerge from the next car, while close behind him was Gerald, with whom, of course, he was unacquainted.
Together they followed him along Sloane Street to Pont Street, where he ascended the steps of a smart-looking red-brick house and opened the door with a latchkey.
"Now that's curious!" remarked Gerald when he rejoined the girl. "Did you notice that he entered that house yonder as though it were his own home? I wonder who lives there?"
"We must find out," declared Marigold, highly excited at having tracked Mr. Boyne so far.
"Yes. But I shall be compelled to watch the house and see what happens now," he said. "I mean to follow him to-night wherever he goes. It almost seems as if he lives here—as well as in Hammersmith!"
"Well—he certainly has a latchkey, and this is not a street where they take in lodgers."
"No," he said. "Some of these houses are the legations of the smaller States of Europe. Over there is the Serbian Legation."
"Well, we'll wait in patience," she said. "Fortunately it's a fine night."
"The last time I watched, last week, it came on terribly wet about eleven o'clock," he said, "and I hadn't my mackintosh. When I started out it seemed a perfect night. But just now the weather is so changeable."