They found him in a discouraging mood. Colonel Watson was dismayed, the inspector triumphant. The inspector was following up a trail of his own and held forth on its possibilities until he realised that Mr. Amberley was not listening to him.
Colonel Watson, more perceptive than the inspector, had been watching Amberley. He said: "You're on to something?"
"I thought I was," Amberley replied. "I still think it. But the only piece of evidence in the whole case hass gone astray and I tell you candidly I'm afraid it may have got into the wrong hands or been destroyed. Where it is I don't know. Until it's found neither you nor I can do anything. Once I get my hands on it you'll have your whole case cut and dried."
The inspector gave a superior smile. "Very fanciful, sir. I suppose it'll clear everything up - Dawson's murder and all? Pity you can't tell us anything now."
There was a glint in Mr. Amberley's eyes. "Since you're so keen on Dawson's murder - a somewhat unimportant link in the chain, as I believe I remarked once before - I'll tell you who did murder him."
The colonel jumped. "You know?"
"I've known since the night of the fancy-dress ball at the manor," said Mr. Amberley calmly. "Collins murdered him."
The colonel stuttered: "But - but…'
"Very nice, sir," said the inspector, still smiling. "A little thing like a good alibi doesn't count, I suppose?"
"You should always beware of alibis, Inspector. If you'd had rather more experience of crime you'd have learned that lesson."