'And this errand took you out of the party at an early stage in the proceedings?'
'Yes. I went off at once, of course. You can't play about with dangerous drugs.'
'And you were absent for nearly four hours?'
'Well, not as long as that.'
'Doctor Tassall, I refuse to credit your story. For one thing, Doctor Matters does his own dispensing. He does not issue prescriptions to be handed in at chemists' shops. Furthermore, it could not possibly have taken you all that time to perform such an errand. Doctor Matters' practice would have to extend to the other side of the County if it had. For your own sake, tell me the truth. I will be plain with you. If I could believe that you had any reason for disposing of Mr Ward, I would subscribe to your immediate arrest, but, so far as I know, you had no motive for that. All the same, you did have a motive for murdering Miss Patterson and doctors have committed murder before this. Come, now. For all we know at present, there may be two murderers in this village and there is nothing, so far, to show that you are not one of them.'
He shrugged his shoulders and decided to make the best of it.
'Oh, well, if you must have it,' he said, 'as I say, I never intended to meet Merle for a showdown. It couldn't do any good. I'd arranged with one of the chaps at the medical school to call me. I'd bought those lizard costumes from him, so I knew he'd oblige me. I had a few dances with Amabel under the disapproving eye of Mrs Kempson, then the chap's call came through. It was an invitation to join a gang of students in a rather low pub in the town. We had a few drinks and then I went back to the chap's room with two or three of the others and we played cards and had a few more drinks until I realised that Merle must have given up and gone home. The Kempson and Conyers tribe would be in bed, I thought, and a clod aimed at Amabel's window would bring her to the front door.'
'Instead of which, you found yourself pulled in to assist in the search for Miss Patterson. I cannot understand why you did not come out with this story at the beginning. Surely you realised that it gave you an alibi for the time of Miss Patterson's death?'
'I didn't realise at first that I needed an alibi. I'd committed myself to this story about being called out to a maternity case and I thought Amabel and her people, especially Mrs Kempson, would take a very dim view if they knew I'd left the birthday party to go on a toot with the lads. I couldn't have let Amabel know, either, that I'd agreed to a tête-à-tête with Merle out in the grounds. You know what girls are. She'd have thought it was-she'd have thought I was double-crossing her, and that would have been the end of everything.'
I felt that I had the truth from him at last. It remained to check his alibi and this I have done. There is no doubt in my mind that, whatever happened in the case of Mr Ward, young Doctor Tassall had no part in the murder of Merle Patterson unless the medical evidence respecting the time of her death was hopelessly out.
This left me with one obvious suspect, but there were difficulties. Only if we could prove that Nigel Kempson had mistaken Merle Patterson for Lionel Kempson-Conyers did his guilt appear even possible, but it made the death of Mr Ward rather less unaccountable. However, we still had to find the reason, if there was one, for Nigel to want to kill either of them. In no way could he hope to inherit the Hill Manor estate, so it was not possible to determine how the child's death could benefit him. The same fact applied in the case of Mr Ward, even if Nigel had believed that the man who had been murdered was the rightful heir.
All the same, even though the photographer had proved a broken reed in that he had lied about waiting for Nigel to pick him up outside the cinema, it was necessary to reconsider Nigel's statement that he had arrived at the pick-up point and hung about there in his car for about an hour before returning to Hill House.
As in the case of Doctor Tassall, there was a time-lag to be taken into account. To pick up the photographer at eleven, Nigel would need to leave Hill House at least not later than ten-forty. At that time Mrs Kempson was in bed, her daughter and son-in-law had retired to their own quarters, Doctor Tassall had been called away and Merle Patterson was still in the house.
As (presumably) Nigel could not have known that Merle had made an appointment to meet Tassall out in the grounds, he could have mistaken her for Lionel and killed her when he met her on his return. If this had been the case, he might not have gone to the town at all, since, according to the medical evidence, Merle could not have died later than about eleven o'clock and it would have been impossible for him to have driven to town, waited for even the shortest time outside the cinema and
