Mitchell raised the shades in the windows overlooking Q Street and peered outside. No automobile except his own, waiting at the curb, was in sight. Satisfied on that point, he opened the window ever so slightly that he might be sure and hear a car drive up to the door, and then, to occupy his time, he wandered about the room and examined the many pieces of bric-a-brac on the mantel and in cabinets.

One cabinet in particular attracted his attention. It was a fine piece of Florentine workmanship and remarkably well preserved. The floor of the cabinet held miniatures of, presumably, ancestors of Miss Susan Baird, and after a cursory glance at them, Mitchell scanned the articles on the glass shelves. A set of carved ivory chessmen awoke his admiration and observing that the key was in the door of the cabinet he opened it. After examining the little chessmen, he turned his attention to the ivory checkers and then to the two ivory cups for holding dice. The carving on them was very fine and to see them better Mitchell carried them to the gas light.

Glancing at the red dice cup, he was surprised to find cotton stuffed inside it. Setting down the other cup, Mitchell pulled out the layer of cotton and found a small bottle standing upright. It was held in the center of the cup by cotton packed around it. Drawing out the bottle he held it up to the light. It was almost empty. Mitchell pulled out the glass stopper and sniffed at the contents. A distinct smell of bitter almonds caused him to draw in his breath sharply.

“Prussic acid!” he muttered. “By God! And Miss Susan Baird was poisoned with a dose of it.”

There was no label on the small phial. Taking out his handkerchief Mitchell replaced the glass stopper, and wrapped his handkerchief about the phial. Putting it carefully in his pocket, he paused for a moment to take another look at the dice cups, then replaced them in the cabinet. He and two of his assistants had made a complete and searching examination of the parlor immediately after the discovery of the crime. Mitchell was willing to swear that neither cotton nor phial had been in the dice cup then. Who had hidden the incriminating evidence there? Who had had the opportunity to do so? Kitty Baird....

Mitchell frowned heavily as he ran over in his mind the list of callers at the Baird home since the tragedy became known. The house was under surveillance and he felt confident no one had evaded the watchful eyes of his operatives. He dismissed the majority of callers—friends and acquaintances who had left cards and letters of condolence—and his thoughts centered on those whom old Oscar had admitted—Charles Craige, Mr. and Mrs. Benjamin Potter, Edward Rodgers, and Major Leigh Wallace—but to the best of his knowledge the Major had not been inside the Baird house. He had seen Kitty and Wallace arrive that afternoon, but Wallace had departed without entering; therefore, he could not have had an opportunity to secrete the bottle of poison in the ivory dice cup.

But Mitchell’s puzzled expression did not lighten, instead it deepened. He was wrong, Wallace had been in the house after the discovery of the murder, for he had accompanied Dr. Leonard McLean to the house on Monday morning. Could the young officer have slipped unseen into the parlor and concealed the bottle of poison while he, Mitchell, and Coroner Penfield were superintending the removal of Miss Baird’s body from the library to her bedroom?

Bah! the idea was absurd. A man would not return to the scene of a murder with incriminating evidence in his pocket when he had had hours in which to throw away the poison without arousing suspicion. But supposing Wallace had, in the horror of the moment, forgotten the bottle? Mitchell shook his head in disbelief. Whoever perpetrated so cold-blooded and premeditated a crime was not apt to overlook getting rid of the poison at the first opportunity.

With Wallace eliminated, Mitchell turned his thoughts to Kitty’s other callers—Ben Potter and his pretty wife, and Charles Craige, the brilliant lawyer and popular clubman. Mitchell smiled broadly—no possible motive linked them in any way, shape or manner with the crime. Edward Rodgers—Mitchell frowned as Mrs. Parsons’ confidences recurred to him. Whatever his connection with the Holt will case, nothing had occurred to associate Rodgers with the murder of Miss Baird. The fact that he was madly in love with her niece was patent to all, but it did not constitute evidence that he had a hand in murdering her aunt.

The exhaust from an automobile broke the stillness and Mitchell paused only long enough at the window to see that a car had stopped near his. The next second he was hurrying down the terraced steps, his mind made up. Kitty had quarreled with her aunt on Sunday afternoon; she had inherited her wealth, and she had had the greatest opportunity to slip the bottle of prussic acid into its hiding place unknown to any one. There were questions which Kitty alone could answer, and she must answer them immediately.