“I know Carver’s theory,” interrupted the chief. “He thinks that the murderer made a mistake in the first instance and intended leaving the pistol behind with the idea of conveying the impression that Trasmere committed suicide. He would have been more clever than that; he certainly would not have shot him in the back. No, there is the fact. I was discussing it with a lawyer only last night, and he agreed with me. The murderer who killed these two unfortunate fellows is determined that there shall be no conclusive evidence against him and there will be none until you can prove how that key came to get on the table after the door had been locked from the outside.

“Now, Holland,” his manner was very serious, “there is certain to be terrible trouble over this crime and somebody is going to be badly hurt unless the murderer is brought to justice. That somebody will be your friend Carver, who, presumably, is in charge of this case and was in charge of the other. I like Carver,” he went on, “but I must join with the hounds that will put him down, unless he can give us something more than theories. And you are in it, too,” he tapped Tab’s chest with a plump forefinger, “head, heels and eyebrows! You are in it from my point of view, especially because it is your job to show the police just where they are wrong, and you have had exceptional opportunity. I am not going to say what will happen to you if you don’t get the biggest story of your life out of this murder, because I don’t believe in threatening a man who may fall down here, and come up smiling on another case, and anyway you are too good a man to threaten. But we’ve got to get this crime cleared up, Holland.”

“I realise that, sir,” said Tab.

“And it will be cleared,” said the editor, “when you have discovered how that key got on the table. Don’t forget that, Holland. Mark that! Puzzle your young brain and get me a solution of that mystery and all the other mysteries will be cleared up.”

Tab knew that Carver was still at Mayfield; he had gone back there after inspecting the rack and ruin left by the burglar in Doughty Street, and Tab went straight on from the office to find, as he expected, that Inspector Carver had by no means completed his investigation.

“The pins are different,” were his first words.

The bright little articles were lying on the table before him, and Tab saw at a glance that one was shorter than the other.

“I wonder if our friend missed it,” said Carver. “He must have done so on this occasion though he probably overlooked the loss on the first murder. Anyway, what is a pin, more or less,” he added moodily. “Come down to the vault, Tab.”

The door of the strong-room was open and the light was burning when Tab went in. He looked at the second stain on the floor, and, despite his excellent nerves, shuddered.

“No weapon was found—he did not even attempt to fake a suicide.”