Ross headed him off.

"Give in, von Ruhle!" he challenged.

The spy recognized the voice of the British lad whom he imagined to be
miles away, on board an unterseeboot.

With a quick movement, the spy plucked a leather case from his coat
pocket and hurled it over the edge of the quay, then, throwing up his
arms, he dropped lifeless upon the rain-sodden ground.

Rapidly a crowd collected. Amongst them was Detective-inspector
Ferret, who, having finished his conversation with his luckless
confrere, was leaving the post office when he heard the commotion.

"Well, what's all this?" he asked brusquely. He bent over the body of
the spy and flashed a pocket-lamp upon his face. "It's our man," he
continued, addressing the lads in an undertone. This remark was
needless, since they were already certain upon that point. "He's done
us out of a job. Heart disease? No fear: it's poison. Don't wait
here. Your work in this direction is done. I have still a few
unpleasant tasks to perform. Cut off to the hotel and await me there.
I may be an hour."

"One moment," protested Vernon. "We saw von Ruhle heave something over
the quay. It might float; if so, there might be a chance to pick it up
by means of a boat. The tide is almost slack. If it has sunk it will
be a diver's task to recover it."

"'Something' is always unsatisfactory," remarked Ferret reprovingly.
"Was it large, small, heavy, or light?"

"He was so jolly quick that I could hardly see it," replied Haye. "I
should think it was about the size of a cigar-case."

Directing two policemen to remove and take charge of the body, the
Detective-inspector accompanied the lads to the edge of the quay. It
was dead low water. There was hardly sufficient current coming down
the Stour to swing the anchored craft against the wind. Then the
investigators made a discovery. Although there was a good depth of
water at the greater extent of the quay, at this spot the mud was
uncovered at the base of the wall, while almost at their feet was a
flight of stone steps.

Ferret descended cautiously and switched on the light of the torch.
Almost within arm's length, and partly buried in the slime, was the
object which the spy had thrown away.

As the detective hooked at it with his stick a hoarse voice shouted:

"Ahoy there! What are you doing with that light?"

Apparently from nowhere a boat ploughed through the mud until its bows
were within a couple of feet of the s