But then what motive could have prompted suicide? Why should a woman so near the grave take her own life? Miss Baird had abhorred illness in any form; she had always had a healthy distaste for invalidism, and little patience with neurotic friends.

Miss Susan Baird, of all persons, to be found dead—possibly murdered! McLean took out his handkerchief and passed it over his forehead. For the first time he grew conscious of the closeness of the atmosphere, of the musty smell which dampness sometimes engenders. Instinctively, he stopped in front of a side door which opened on a “stoop” leading to the garden which extended to the back of the house. The door resisted his attempts to open it, and he felt for the key. It was not in the lock.

McLean stared at the door in some surprise. It was the only one in the house fitted with a modern lock, and it had always been Miss Baird’s custom to leave the key in the lock. The locks of the other doors were hand-wrought before the Revolution and massive in size. It had been Miss Baird’s fad never to have them modernized. One of her few extravagances, if it could be called such, had been to employ a grandson of old “Oscar,” their colored factotum, to keep the copper highly burnished and shining with its old-time, slave-day luster. The great fireplaces were lined with copper and Miss Baird was never happier than when able to contemplate her grotesque reflection in the walls of the fireplace in her library.

McLean had been a frequent visitor at the Baird mansion, but never before had he seen the key removed from the side door of the library. With a puzzled frown he reached up and pulled back the copper latch which released the upper half of the door—built in the style of the “Dutch” door—and pulled it back. The fresh air, laden as it was with dampness, was refreshing. The rain had slackened, and seeing there was no danger of it splashing inside the library, he pulled the half door still further open. Turning about, he found Inspector Mitchell at his elbow.

“I caught Mr. Craige,” he announced. “He is coming right over.” Then with a complete change of tone. “How did you open the upper half of this door?”

“By pushing the catch, so—” and McLean demonstrated.

“Hump!” Inspector Mitchell moved the catch back and forth. “I see, there’s a knack about it; it baffled me when I tried to open it. I have the key of the lower door,” and he drew it out of his pocket.

“Why did you take it out of the lock?”

“Because—” Inspector Mitchell’s answer was interrupted by the sudden rush of feet across the outer hall. The portières were thrust aside and a girl dashed into the library followed by a man.