‘A very singular thing to do, Dr Abbershaw,’ he said. ‘And may I ask where you got this wallet?’

Abbershaw hesitated. For the moment he was in a quandary. If he told the truth he could hardly help incriminating Campion, and in view of that young man’s present condition it was inhuman to betray him.

‘I found it,’ he said at last, realizing at once how lame the explanation must sound. Gideon shrugged his shoulders. ‘This man is wasting our time,’ he said. ‘No, it is Petrie you should examine, as I have told you all along. He’s just the type they would choose. What shall we do with these two?’

‘Put them in the other room – not the one the young lunatic got out of,’ said Dawlish. ‘You came through the passage from the fire-place in the hall, I suppose,’ he added, turning heavily to Abbershaw, who nodded. ‘We must wait for Whitby to see this case,’ he continued, ‘then we will consider what is to be done.’

The stranger who had been standing at Meggie’s side laid a hand on her shoulder.

‘Come,’ he said, jerking her to her feet.

Abbershaw turned on him furiously, only to find a revolver pressed against his ribs. They were heading towards the staircase behind the fire-place by which he had come, but when they reached the threshold Dawlish spoke again.

‘Dr Abbershaw,’ he said, ‘come here.’

Unwillingly, the young man turned and stood before the desk, looking down at the florid Teutonic face with the dull corpse-like eyes.

‘So you are an expert often referred to by Scotland Yard.’