a week, owing to the discovery of a hostile mine-field off
the Dutch coast. Sailings were to be resumed that night. A man who
gave himself out to be a Dutchman, but who answered to the description
of von Ruhle, had applied that morning for a permit to leave the
country by the night boat. His berth had been booked under the name of
Cornelius Vanderhuit.

"Which one ought we to nab first?" asked Ferret. "We'll have to be
very sharp, or one of them, finding that he is no longer in
communication with his accomplice, would smell a rat and clear out."

"Under normal conditions I would reply, 'Collar the principal first',"
replied Hawke. "It is evident that Ramblethorne, _alias_ von
Hauptwald, is the master-spy. Directly he's laid by the heels, the
whole of the organization immediately under his control goes by the
board. But there's this Harwich business. Von Ruhle crosses the North
Sea to-night, unless otherwise prevented. We comprise the otherwise, I
hope."

"Then it would mean catching the midday express to Waterloo," remarked
Ferret.

"Could we go with you?" asked Ross.

The police officers looked rather astonished at the cool request. Like
most professional men, they scouted the idea of amateur assistance when
the main issue was at stake.

"Perhaps it wouldn't be a bad idea," remarked Hawke. "You have already
shown great discretion in the matter. Most fellows would have made a
bee-line to the nearest telegraph office and given the whole show away.
The only difficulty is--I suppose, by the way, you are not feeling too
done up after your trying experiences?--the only difficulty is, I was
remarking, that von Ruhle might spot you. Look here, Ferret; suppose
you take these young gentlemen, and proceed to Harwich by an ordinary
train? Keep well out of sight when you arrive at Parkeston Quay, but
keep a sharp eye on the boat. I'll travel from Liverpool Street by the
boat train, and see if I can pick out our quarry amongst the
passengers."

It was a tedious journey from Plymouth to Harwich. Arriving at
Waterloo, Ferret took the lads to a quiet hotel and ordered lunch;
while Hawke, excusing himself, called in at "the Yard" to report his
new case to the Chief, and to wait for the Great Eastern boat train.

The weather had changed completely during the run from the West, for
when Ferret and the two lads arrived at Parkeston Quay it was raining
heavily, accompanied by half a gale of wind from the east'ard.