mouth writhed in sinuous curves. He commenced to puff. The water
bubbled unevenly.

Garth examined the rugs with growing excitement. He was prepared to
believe that he had stumbled on a meeting place. And after all wasn't
this an ideal rendezvous? The shop had probably been here for years. The
town was full of such stores. At any rate his impression of a calculated
evil increased. He felt himself the object of suspicion. It was
conceivable to him that he might suffer a fate similar to
Brown's--perhaps behind that hideous curtain which the Levantine and the
cross-legged figure seemed to guard.

Garth started. The unequal bubbling of the pipe had accompanied all his
thoughts. Constantly it would pause, then recommence. The idea which had
been struggling unconsciously in the detective's brain took shape. That
uneven bubbling possessed a significance beyond the pleasures of
nicotine. It suggested a means of communication, a code.

While he bargained with the Levantine his confidence in this eccentric
explanation increased. It condemned the occupants of the shop. Whether
or not the men were connected with the plot Brown had feared against
Alsop, they were decidedly objects of interest to the police. Still, if
Brown had spied here, the danger was obvious. The Levantine and the man
in the fez were sinister opponents. Yet Garth wanted to see behind that
grotesque curtain.

For a time, listening to the bubbling, he wondered if they would let him
leave the shop at all. He was in no hurry to go until he had made sure
of one or two things. While fingering a rug he managed stealthily to
examine the wall. It was about what he had hoped, what he had expected.
The house was very old. It was one of a row built simultaneously before
the fire laws had amounted to much. He was sure that the dividing walls
between these basements were not fireproof. As nearly as he could tell
from the surface he examined, they would probably be lath-and-plaster,
with, perhaps, rubble in the space between. His next step was to measure
as accurately as he could with his eye the distance between the entrance
and the curtain, which was like a ceremonial background for the man in
the fez. Stooping to inspect one of the rugs, he struck the flooring
with his fist, as if by accident. He was satisfied. There was no cellar
beneath this basement. He dared hope that he would see what lay behind
the curtain.

Approximating as nearly as he could the subtleties of a