The Chestermarke Instinct by J.S. Fletcher

Neale was instantly awake and on the alert. He sprang to his feet, shivering a little in spite of the rugs which he had wrapped about him before settling down. A slight current of cold air struck him as he rose -- looking in the direction from which it seemed to come, he saw that one of the circular windows in the high wall above him was open, and that a fresh north-east wind was blowing the curtain aside. The laboratory, hot and close enough when he had entered it the previous evening, was now cool; the morning breeze freshened and sharpened his wits. He pulled out his watch, which he had been careful to wind up before lying down. Seven o'clock! -- in spite of his imprisonment and his unusual couch, he had slept to his accustomed hour of waking.

Knowing that Joseph Chestermarke might walk in upon him at any moment, Neale kept himself on the look out, in readiness to adopt a determined attitude whenever he was discovered. By that time he had come to the conclusion that whether force would be necessary or not in any meeting with Joseph, it would be no unwise thing to let that worthy see at once that he had to deal with an armed man. He accordingly saw to it that his revolver, already loaded, was easily get-at-able, and the flap of his hip-pocket unbuttoned: under the circumstances, he was not going to be slow in producing that revolver in suggestive, if not precisely menacing fashion. This done, he opened his box of chocolate, calculated its resources, and ate a modest quantity. And while he ate, he looked about him. In the morning light everything in his surroundings showed clearly that his cursory inspection of the night before had been productive of definite conclusions. There was no doubt whatever of the character of the mysterious door set so solidly and closely in its framework in the blank wall: the door of the strong room at Chestermarke's Bank was not more suggestive of security.