"Because in my judgment those books were not books at all in the usually understood sense. Unless I am at fault, the parcel contained three big ledgers glued together, the contents being hollowed out and that hollow filled with thermite, a clockwork detonator, or the necessary electric apparatus to start a spark at a given moment." The accountant stared at him. "You're joking," he said, but Tarling shook his head. "I was never more serious in my life." "But who would commit such an infernal act as that? Why, one of my clerks was nearly burnt to death!" "The man who would commit such an infernal act as that," repeated Tarling slowly, "is the man who has every reason for wishing to avoid an examination of Lyne's accounts." "You don't mean----?" "I'll mention no names for the moment, and if inadvertently I have conveyed the identity of the gentleman of whom I have been speaking, I hope you will be good enough to regard it as confidential," said Tarling, and went back to his crestfallen subordinate. "No wonder Milburgh was satisfied with the forthcoming examination," he said bitterly. "The devil had planted that parcel, and had timed it probably to the minute. Well, there's nothing more to be done to-night--with Milburgh." He looked at his watch. "I'm going back to my flat, and afterwards to Hertford," he said. He had made no definite plan as to what line he should pursue after he reached Hertford. He had a dim notion that his investigation hereabouts might, if properly directed, lead him nearer to the heart of the mystery. This pretty, faded woman who lived in such style, and whose husband was so seldom visible, might give him a key. Somewhere it was in existence, that key, by which he could decipher the jumbled code of the Daffodil Murder, and it might as well be at Hertford as nearer at hand. It was dark when he came to the home of Mrs. Rider, for this time he had dispensed with a cab, and had walked the long distance between the station and the house, desiring to avoid attention. The dwelling stood on the main road. It had a high wall frontage of about three hundred and fifty feet. The wall was continued down the side of a lane, and at the other end marked the boundary of a big paddock. The entrance to the grounds was through a wrought-iron gate of strength, the design of which recalled something which he had seen before. On his previous visit the gate had been unfastened, and he had had no difficulty in reaching the house. Now, however, it was locked.