“It would be advisable, I think,” said the detective, as he picked up the other volumes and replaced them in the bookcase. “Is there anything more I can do for you, professor? You will pardon me if I say that I am very busy, and that it is getting late.”

“My dear Mr. Carter, I am sorry I have disturbed you. I apologize most sincerely. Good night!”

He walked to the door, opened it, turned to bow and smile, and went down the stairs.

Nick Carter waited till he heard the front door close after the professor, and turned to Chick. But it was unnecessary for him to say anything. Chick nodded comprehendingly, and leaped down the stairs three or four at a time. Then he dashed along the hall and out to the street.

“I’ll go, too,” muttered Nick, as he also ran down the stairs and to the outer air.[Pg 17]

He had only just got off the stone steps and turned to the darkness on the left, when he heard a muffled cry from somebody, followed by a scraping on the sidewalk and the sound of something falling heavily.

“Chick!” he called.

There was no answer, and Nick Carter felt a strange premonition of evil. He ran down the avenue for perhaps a hundred feet. Then, as he stumbled over something soft that was lying across the sidewalk, he knew that his premonition was not without foundation.

Chick was stretched out, unconscious. The detective turned the light of his pocket flash upon him and gave vent to a shout of horror.

Sticking in the sleeve of his insensible assistant were two long needles, crossed!