"Well, sir," began the former, with smiling importance, "and
what may--?"

Valentin pointed suddenly with his cane. "I'll tell you on
the top of that omnibus," he said, and was darting and dodging
across the tangle of the traffic. When all three sank panting on
the top seats of the yellow vehicle, the inspector said: "We could
go four times as quick in a taxi."

"Quite true," replied their leader placidly, "if we only had
an idea of where we were going."

"Well, where are you going?" asked the other, staring.

Valentin smoked frowningly for a few seconds; then, removing
his cigarette, he said: "If you know what a man's doing, get in
front of him; but if you want to guess what he's doing, keep
behind him. Stray when he strays; stop when he stops; travel as
slowly as he. Then you may see what he saw and may act as he
acted. All we can do is to keep our eyes skinned for a queer
thing."

"What sort of queer thing do you mean?" asked the inspector.

"Any sort of queer thing," answered Valentin, and relapsed
into obstinate silence.

The yellow omnibus crawled up the northern roads for what
seemed like hours on end; the great detective would not explain
further, and perhaps his assistants felt a silent and growing doubt