Nick Carter Stories No. 148, July 10, 1915; The Mark of Cain; or, Nick Carter's Air-line Case

Issued Weekly. Entered as Second-class Matter at the New York Post Office, by Street & Smith, 79-89 Seventh Ave., New York. Copyright, 1915, by Street & Smith. O. G. Smith and G. C. Smith, Proprietors.
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No. 148. NEW YORK, July 10, 1915. Price Five Cents.
Edited by CHICKERING CARTER.
The girl at the switchboard held her breath. The detective waiting in the business office saw her. The girl at the switchboard was Helen Bailey. The waiting detective was Nick Carter.
No man was ever more quick than he to rightly interpret a facial expression. The partition through which he saw her was of glass, or a portion of it, dividing the general manager’s office in the central telephone exchange from the room in which the great switchboards were stationed.
There were other girls, half a score of them, seated in front of the innumerably perforated boards. They were too busy to notice one another. Their eyes were intent upon their work. Their deft hands flew from plug to plug, withdrawing some, inserting others. Their frequent, monotonous calls, the noise of the buzzers and the snapping of the rubber-covered plugs were the only sounds to be heard in that busy room.