Inspector Dunbar stood in the little dispensary tapping his teeth with
the end of a fountain-pen.

"The last time he visited you, doctor--the time when he gave you the
envelope--did the cabman wait here in the waiting-room?"

"He did--yes. He came after my ordinary consulting hours and I was at
supper, I remember, as I am compelled to dine early."

"He would be in here alone?"

"Yes. No one else was in the room."

"Would he have had time to find the box, cut out the piece of
cardboard from the lid, put it in the envelope and seal it?"

"Ample time. But what could be his object? And why mark the envelope
30?"

"It was in your consulting-room that he asked you to take charge of
the envelope?"

"Yes."

"Might I take a peep at the consulting room?"

"Certainly, Inspector."

From the waiting-room they went up a short flight of stairs into the