rything found, with its exact position. The elaborate trouble taken
by these men to describe minutely in writing every little thing would
have seemed absurd to any one not versed in the ways of the Criminal
Investigation Department. Yet nothing was done that was not necessary.
An error of an inch in a measurement might make all the difference when
the case came on for trial.

Foyle and Green left the house in charge of the divisional man. Already
a description had been circulated of the man they had failed to
surprise; but as neither had caught more than a glimpse of a shadowy
figure in the darkness, they had had to rely on the descriptions given
by Israels and his wife. And even if that estimable pair had really
tried honestly to give a fair description of the man--which the
detectives thought was extremely doubtful--there could be little hope
that it was accurate. If the average man tries to describe the
appearance of his most intimate friend and then asks a stranger to
identify him, he will realise how misleading such descriptions may be
even at the best of times. Yet the Criminal Investigation Department had
to work with such material as they had.

Heldon Foyle was very silent as they trudged side by side out of
Whitechapel into the silent City streets--for there are no taxicabs to
be found in the East End at such hours. The case was developing; but
though he was beginning to have a hazy glimpse into some of its
workings, there was much that remained a mystery to him. His
questionings of Israels had satisfied him that the man who had escaped
was neither Grell nor Ivan. He could not blame himself for not effecting
an arrest. Looking back over the night's events, he could not see that
he could have taken further precaution. If he had taken more men the
escape would have occurred just the same over the roofs, for he would
still have felt it his duty to question Israels. He could not have
foreseen that the ready-witted Lola was there, nor that she should have
so ingeniously given the alarm. The luck had been against him.

Nevertheless he had gained an important fact. Lola was in London and was
obviously acting in concert with Grell. It was easier to look for two
persons than one. Sooner or later he would lay hands on them and solve
the mystery of the murder. He clenched his fists resolutely as his
thoughts carried him away. Meanwhile there was the cipher. If that could
be de-coded it might be valuable.

Green's voic