He held up the knife with which Arthur Fane had been stabbed. It still bore, at a distance, resemblance to a rubber one.
"The ironmonger's willing to identify the person who bought it. That was a bad bloomer on our friend's part. But it always happens. These clever people will do it."
Masters put down the knife, and picked up an official cellophane envelope containing traces of a whitish powder.
"Finding the stuff itself, in the place where we did find it. Lummy! That's the best yet. So far as I'm concerned personally, or a jury's concerned, that's hanging evidence. But, sir, the case isn't complete. It's all very well to say, 'Write out your warrant.' We can't make out one, and the chief constable can't sign it, until we know how the ruddy knife was used, and how the person in question managed to exchange it with the toy one in full view of all the other witnesses."
"Oh, that?" murmured H.M., as though completely uninterested.
Masters pushed his chair away from the desk. His temper was simmering again.
"Oh, that?" he mimicked. "I suppose you don't think that's important?"
"It's important. Sure. But it's not difficult."
"No? You just tell me how it was done — tell me a practical way — and I'll have our friend in chokey before you can say Jack Robinson. The poison-in-the-grapefruit part of the thing, I admit, is easy. That's just what we thought it must be. But the dagger business has got me up a tree, and I don't mind saying so."
H.M. looked distressed.