The detective eyed him thoughtfully, as if he were hunting for the answer to a riddle.
'No. Not yet. Nothing definite.'
'I presume you take it for granted it was the work of a professional burglar.'
'No. No. Take nothing for granted. Great mistake. Prejudices one way or other great mistake. But, I think, yes, I think it was probably—almost certainly—not done by a professional.'
Mr Thompson looked rather blank at this. It shook his confidence in his powers of deduction.
'But,' he expostulated. 'Surely no one but a practised burglar would have taken a pane of glass out so—ah—neatly?'
Inspector Roberts rubbed a finger thoughtfully round the place where the glass had been. Then he withdrew it, and showed a small cut from which the blood was beginning to drip.
'Do you notice anything peculiar about that cut?' he enquired.
Mr Thompson did not. Nor did the ground-man.
'Look carefully. Now do you see? No? Well, it's not a clean cut. Ragged. Very ragged. Now if a professional had cut that pane out he wouldn't have left it jagged like that. No. He would have used a diamond. Done job neatly.'