"Let me trace the connections of events.

"The first link in the chain was a visit that I had paid in my younger
days to Moscow and Warsaw, where I had stayed long enough to acquire a
useful knowledge of Russian and Yiddish. The second link was the failure
of my plan to lure the murderer of my wife--and, incidentally, other
criminals--to my house. The trap had been scented not only by the
criminals but also by the police, of whom one had visited my museum with
very evident suspicion as to the nature of my specimens.

"After the visit of the detective, I was rather at a loose end. That
unknown wretch was still at large. He had to be found and I had to find
him since the police could not. But how? That detective had completely
upset my plans and, for a time, I could think of no other. Then came the
dirty rascal who had tried to murder me in the chalk-pit; and from his
mongrel jargon, half cockney, half foreign, I had gathered a vague hint.
If I could not entice the criminal population into my domain, how would
it be to reconnoiter theirs? The alien area of London was well known to
me, for it had always seemed interesting since my visit to Warsaw, and,
judging from the police reports, it appeared to be a veritable happy
hunting-ground for the connoisseur in criminals.

"Hence it was that my unrest led me almost daily to perambulate that
strange region east of Aldgate where uncouth foreign names stare out
from the shop signs and almost every public or private notice is in the
Hebrew character. Dressed in my shabbiest clothes, I trudged, hour after
hour and day after day, through the gray and joyless streets and alleys,
looking earnestly into the beady eyes and broad faces of the
East-European wayfarers and wondering whether any of them was the man I
sought.