had seen that lorry a
hundred times I should never have suspected a tank. It's well designed."

They turned to examine the other vehicles. All four were identical
in appearance with the first, but all were strictly what they seemed,
containing no secret receptacle.

"Merriman said they had six lorries," Willis remarked. "I wonder where
the sixth is."

"At the distillery, don't you think?" the Frenchman returned. "Those
drops prove that manager fellow has just been unloading this one. I
expect he does it every night. But if so, Raymond must load a vehicle
every night too."

"That's true. We may assume the job is done every night, because
Merriman watched Coburn come down here three nights running. It was
certainly to unload the lorry."

"Doubtless; and he probably came at two in the morning on account of his
daughter."

"That means there are two tank lorries," Willis went on, continuing his
own line of thought. "I say, Laroche, let's mark this one so that we may
know it again."

They made tiny scratches on the paint at each corner of the big vehicle,
then Willis turned back to the office.

"I'd like to find that cellar while we're here," he remarked. "We know
there is a cellar, for those Customs men saw the Girondin loaded from
it. We might have a look round for the entrance."

Then ensued a search similar to that which Willis had carried out in
the depot at Ferriby, except that in this case they found what they were
looking for in a much shorter time. In the office was a flat roll-topped
desk, with the usual set of drawers at each side of the central knee
well, and when Willis found it was clamped to the floor he felt he
need go no further. On the ground in the knee well, and projecting out
towards the revolving chair in front, was a mat. Willis raised it,
and at once observed a joint across the boards where in ordinary
circumstances no joint should be. He fumbled and pressed and pulled, and
in a couple of minutes he had the satisfaction of seeing the floor under
the well rise and reveal the head of a ladder leading down into the
darkness below.

"Here we are," he called softly to Laroche, who was searching at the
other side of the room.

The cellar into which the two detectives descended was lined with timber
like that at Ferriby. Indeed the two were identical, except that only
one passage--that under the wharf--led out of this one. It contained a
similar large tun with a pipe leading down the passage u