The first person whose image came to Dick's mind was Abel Death. The image immediately suggested a train of circumstance which, in the heat of the moment, proclaimed the absent man guilty. Abel Death had made his appeal to Samuel Boyd, and had made it in vain. In a paroxysm of fury he had fallen upon his master, and had strangled him. Then, searching for money and finding it, he had fled from the house and taken passage in some outgoing vessel for a foreign land. Presuming that the murder had been committed on the night of the 1st of March there had been ample time to make his escape, but not sufficient time to communicate with his wife. Or, perhaps the man, overwhelmed by terror, was afraid to write. But upon further reflection this train of circumstance fell apart, and Dick perceived how false it was. It was hardly probable that Samuel Boyd had received Abel Death while he was abed, and still less probable that in his sleeping attire he would open his street door to such a visitor. By no other means than through the door could Abel Death have obtained access to the house. No, it was not he who had committed the crime. But the man was gone, and the mystery of his disappearance was still unexplained. But if Abel Death could have obtained access to the house only by permission of Samuel Boyd, there was another man who had no need to ask for it. That man was Mr. Reginald Boyd. He possessed a key to the street door, and could obtain admittance at any hour. At any hour? No. Not after Samuel Boyd had chained and bolted the door from within before he went to bed. What was the presumption? That Reginald had quietly entered before the door was fastened, and had secreted himself until his father had retired to rest. Easy to imagine what followed: his appearance in the bedroom when his father was half asleep, his demands for money, the stern refusal and the taunting exchange of angry words, the hot blood roused, the clutching his father by the throat, the murder committed, the disposal of the limbs to make it appear that he had died a natural death, the unbolting and unchaining of the street door, and, finally, the frantic flight. But how to account for the key being upon the mat? As Dick mentally asked this question his eyes fell upon a key hanging by a cord at the head of the bed. Was it Samuel Boyd's own private key to the street door? So much depended upon this that Dick hastened downstairs to settle the point. Yes, it was Samuel Boyd's key. And the second key which Dick had picked up? Dropped by Reginald in his frenzy as he flew out of the house.