In less than a quarter of an hour we were walking along Connaught
Road again.

"By the way, what is Dr. Coles's address?" asked Quarles.

I gave it to him. It was a turning off Connaught Road.

"I shall go and see him, and then I have a call to make elsewhere. Come
to Chelsea to-night, Wigan. Take my word for it, criminals are no
cleverer than they used to be."

When I went to Chelsea that evening I found the professor and Zena
waiting for me in the empty room. He was evidently impatient to talk.

"My brain may possibly require oiling, Wigan, but Zena's questions are
just as absurd as they ever were," he began. "She wanted to know why the
lead had been packed so carelessly, and what use a dead body could be to
any one. No bad points of departure for an inquiry. Now, when the coffin
was opened after the knock had been heard, a little sawdust from the
screw holes fell on the carpet. It was there when we went into the room
this morning. We may reasonably argue that some sawdust must have fallen
when the coffin was opened during the night. But no one seems to have
noticed it."

"It might easily have escaped casual notice even if the thieves neglected
to remove it, which is unlikely," I returned.

"It would not be so easy to remove, for the carpet is a thick one, and
the thieves would be in a hurry, you know. Also there were wreaths about