"How's that?" inquired Average Jones.

The other took an envelope from his pocket and handed it over. "It
got enclosed by mistake with the copy for the advertisement. The
handwriting on the envelope is his own. Look inside."

A glance had shown Average Jones that the letter, had been mailed in
New York on March twenty-fifth. He took out the enclosure. It was
a small slip of paper. The date was stamped on with a rubber
stamp. There was no writing of any kind. Near the center of the
sheet were three dots. They seemed to have been made with red ink.

"You're sure the address is in Professor Moseley's writing?"

"I'd swear to it."

"It doesn't follow that he mailed it to himself. In fact, I should
judge that it was sent by someone who was particularly anxious not to
have any specimen of his handwriting lying about for identification.

"Perhaps. What's your interest in all this, anyway my mysterious
young friend?"

"Two dogs in New York poisoned in something the same way as yours."

"Well, I've got my man. He confessed."

"Confessed?" echoed Average Jones.