Poirot himself had had a slight bronchial chill which had prevented his attending. Fortunately he had not insisted on having my company.

‘Committed for trial,’ said Japp. ‘So that’s that.’

‘Isn’t it unusual?’ I asked, ‘for a defence to be offered at this stage? I thought prisoners always reserved their defence.’

‘It’s the usual course,’ said Japp. ‘I suppose young Lucas thought he might rush it through. He’s a trier, I will say. Insanity’s the only defence possible.’

Poirot shrugged his shoulders.

‘With insanity there can be no acquittal. Imprisonment during His Majesty’s pleasure is hardly preferable to death.’

‘I suppose Lucas thought there was a chance,’ said Japp. ‘With a first-class alibi for the Bexhill murder, the whole case might be weakened. I don’t think he realized how strong our case is. Anyway, Lucas goes in for originality. He’s a young man, and he wants to hit the public eye.’

Poirot turned to Thompson.

‘What’s your opinion, doctor?’

‘Of Cust? Upon my soul, I don’t know what to say. He’s playing the sane man remarkably well. He’s an epileptic, of course.’

‘What an amazing dénouement that was,’ I said.

‘His falling into the Andover police station in a fit? Yes—it was a fitting dramatic curtain to the drama. A B C has always timed his effects well.’

‘Is it possible to commit a crime and be unaware of it?’ I asked. ‘His denials seem to have a ring of truth in them.’

Dr Thompson smiled a little.

‘You mustn’t be taken in by that theatrical “I swear by God” pose. It’s my opinion that Cust knows perfectly well he committed the murders.’

‘When they’re as fervent as that they usually do,’ said Crome.

‘As to your question,’ went on Thompson, ‘it’s perfectly possible for an epileptic subject in a state of somnambulism to commit an action and be entirely unaware of having done so. But it is the general opinion that such an action must “not be contrary to the will of the person in the waking state”.’

He went on discussing the matter, speaking of grand mal and petit mal and, to tell the truth, confusing me hopelessly as is often the case when a learned person holds forth on his own subject.

‘However, I’m against the theory that Cust committed these crimes without knowing he’d done them. You might put that theory forward if it weren’t for the letters. The letters knock the theory on the head. They show premeditation and a careful planning of the crime.’

‘And of the letters we have still no explanation,’ said Poirot.

‘That interests you?’

‘Naturally—since they were written to me. And on the subject of the letters Cust is persistently dumb. Until I get at the reason for those letters being written to me, I shall not feel that the case is solved.’

‘Yes—I can understand that from your point of view. There doesn’t seem to be any reason to believe that the man ever came up against you in any way?’