“Mr. Ludgrove told me this, and I thought it wouldn’t do him any harm to go and look for these collycums, or whatever he calls them,” broke in Whyland. “Besides, his suggestion gave me an idea. So we smuggled him off to Paddington, where two of my plain clothes men saw him into a train on Saturday morning. I reckoned he’d be safe enough out of London. Then I stayed here, being careful to keep a light burning in the shop, so as people would think Mr. Ludgrove was in residence. Then we met Mr. Ludgrove’s train at Paddington yesterday, evening, and brought him back. But, as I say, nothing happened. I only had one visitor all the time, and that was young Copperdock, on Sunday morning. I explained to him that Mr. Ludgrove was upstairs, and he said he would look in again later. But he never came, at least while I was here.”

“Well, it wasn’t a bad notion, certainly,” said Hanslet. “I don’t think I should go about alone too much, if I were you, Mr. Ludgrove.”

The herbalist smiled. “I hardly get the chance,” he replied. “I have a habit of taking a brisk walk in the neighbourhood every evening. During this last week I have never gone more than a few steps before being accosted by a charming and talkative individual who insists upon accompanying me. I am not complaining, I have found his conversation most interesting.”

“And he yours, Mr. Ludgrove,” laughed Whyland. “I’m sorry, but what can we do? I don’t want to alarm you, but you know there is the chance that an attack might be made upon you. And that attack would give us the clue we want.”

“I see. I am to be used as a stalking-horse,” said Mr. Ludgrove. “Well, I have no objection. I am only too glad to be of service in unravelling this terrible mystery.”

Hanslet, who had been silent for a moment or two, suddenly turned towards Whyland. “You say that nobody came near you while you were alone here but young Copperdock. What did he want, I wonder? Have you seen him since you came back from your herbalizing expedition, Mr. Ludgrove?”

A grave expression spread over the herbalist’s face. “I have,” he replied. “It was for this reason that I asked Inspector Whyland to come here and see me. I was about to tell him the story when you came in, and I realized that it would be better if you heard it together. Ted Copperdock came here yesterday evening, about an hour after my return.”

“Oh, he did, did he!” exclaimed Hanslet. “What did he want?”

“He told me he had come round in the morning to ask me if I would go through his father’s belongings with him. Finding me busy, as he supposed, he went back home, and started to go through them by himself. He spent the whole afternoon sorting out Mr. Copperdock’s papers, and it was not until late that he began to look over his clothes. In the pocket of one of his coats he discovered something which, as he himself said, terrified him. He came to me at once, and begged me to come back with him. He was so insistent that I broke the promise which I had made to Inspector Whyland, not to go alone into any house in Praed Street, and went upstairs with him into his father’s bedroom. There he showed me an overcoat hanging in a cupboard, and in the pocket of it—this!”

The herbalist rose, walked to the bench at the far end of the room, and pointed to an object wrapped loosely in paper. Hanslet and Whyland followed him, and the former unwrapped the paper carefully. As the object appeared, they both uttered a startled exclamation. It was the blade of a knife, and with it a long wooden handle, with a hole running the whole of its length, and fitted with a set-screw.