‘Very well.’ Knight stood over Trevor and imposed upon himself, evidently with difficulty, an air of sweet reasonableness. ‘If,’ he said, ‘dear boy, you were spying about in front while I was with Mr Morris in his office, and if you heard our voices, you doubtless also saw us leave the theatre.’

Trevor nodded.

‘Precisely,’ Knight said and spread his hands at Alleyn.

‘People come back,’ said the treble voice. Alleyn turned to find Trevor, the picture of puzzled innocence, frowning, his fingers at his lips.

‘What the hell do you mean by that!’ Knight ejaculated.

‘It’s part of what I can’t remember. Somebody came back.’

‘I really cannot imagine, Alleyn – ‘ Knight began.

‘I – don’t – think – I – want – to – remember.’

‘There you are, you see. This is infamous. The boy will be harmed. I absolutely refuse to take part in a dangerous and unwarranted experiment. Don’t worry yourself, boy. You are pefectly right. Don’t try to remember.’

‘Why?’

‘BECAUSE I TELL YOU,’ Knight roared and strode to the door. Here he paused. ‘I am an artist,’ he said suddenly adopting a muted voice that was rather more awful than a piercing scream. ‘In eight hours’ time I appear before the public in a most exhausting role. Moreover I shall be saddled throughout a poignant, delicate and exacting scene with the incompetence of some revolting child-actor of whose excesses I am as yet ignorant. My nerves have been exacerbated. For the past forty-eight hours I have suffered the torments of hell. Slighted. Betrayed. Derided. Threatened. And now – this ludicrous, useless and impertinent summons by the police. Very well, Superintendent Alleyn. There shall be no more of it. I shall lodge a formal complaint. In the meantime – Goodbye.’

The door was opened with violence and shut – not slammed – with well-judged temperance.

‘Lovely eggzit,’ said Trevor yawning and reading his comic.

From outside in the corridor came the sound of applause, an oath, and rapidly retreating footsteps.

Alleyn reopened the door to disclose Harry Grove, gently clapping his hands, and Marcus Knight striding down the corridor.

Harry said, ‘Isn’t he superb? Honestly, you have to hand it to him.’ He drew a parcel from his pocket. ‘Baby roulette,’ he said. ‘Trevor can work out systems. Is it true that this is a sort of identification parade?’

‘You could put it like that, I suppose,’ Alleyn agreed.

‘Do you mean,’ Harry said, changing colour, ‘that this unfortunate but nauseating little boy may suddenly point his finger at one of us and enunciate in ringing tones: “It all comes back to me. He dunnit”.’

‘That, roughly, is the idea.’

‘Then I freely confess it terrifies me.’

‘Come inside and get it over.’