“I examined his hands, sir; and in the right one, I found something important. The hand was clenched, and when I got it open at last, this fell out.”
He produced a button with a shred of cloth attached to it, which he laid on the desk before Sir Clinton. The Chief Constable picked it up, examined it closely, and then, pulling out a pocket magnifying glass, made a still more minute inspection.
“Very interesting, Inspector. What do you make of it?”
“Obviously it was torn off the murderer's clothes during the struggle, sir. And I've seen something like it before. You see that canary-coloured stain on the bit of cloth and also on the threads that hold the button to the fabric?”
“Dyed with picric acid, by the look of it, I should say. Is that what you mean?”
“Yes, sir. And the pattern of the cloth's another point.”
“You mean it looks like a button torn off the old jacket that Silverdale was wearing, that day we saw him at the Croft-Thornton Institute—his laboratory coat?”
“That's undoubtedly what it is, sir. I remember that stain perfectly. And as soon as I saw it, I remembered the pattern of the cloth.”
“And your view is?”
“I think that when Silverdale set out to murder Whalley he was afraid that some blood from the face might get on to his coat. So he put on his old laboratory jacket. If it got spotted, he could destroy it and rouse no suspicions. It was only an old coat that he might think was worn out. Quite a different thing from destroying some of his ordinary clothes. That would have been suspicious. But an old coat—no one would wonder if he got rid of it and brought another one down to the laboratory to replace it.”