I said, 'Maybe I'd better take this up at a higher level; perhaps with your Chairman.'

'As you wish,' said Isaacson in a cold voice.

I decided to lower the temperature myself. 'Just one more thing, Mr Isaacson. When Mr Hoyland asks you for information you do not – repeat not – tell him that what he wants to know is no concern of security. You give him all the information you have, as you have given it to me. I hope I make myself clear?'

'Very clear.' Isaacson's lips had gone very thin.

'Very well; you will allow Mr Hoyland access to everything concerning Billson, especially his salary record. I'll have a word with him before I leave.' I stood up. 'Good morning, Mr Isaacson.'

I checked back with Hoyland and told him what I wanted, then went in search of the Widow Harrison and found her to be a comfortable motherly old soul, supplementing her old age pension by taking in a lodger. According to her, Billson was a very nice gentleman who was no trouble about the house and who caused her no heart-searching about fancy women. She had no idea why he had left and was perturbed about what she was going to do about Billson's room which still contained a lot of his possessions.

'After all, I have a living to make,' she said. 'The pension doesn't go far these days.'

I paid her a month in advance for the room and marked it up to the Franklin Engineering account. If Isaacson queried it he'd get a mouthful from me.

She had not noticed anything unusual about Billson before he walked out. 'No, he wasn't any different. Of course, there were times he could get very angry, but that was just his way. I let him go on and didn't take much notice.'

'He was supposed to go to work last Monday, but he didn't. When did you see him last, Mrs Harrison?'

'It was Monday night. I thought he'd been to work as usual. He didn't say he hadn't.'

'Was he in any way angry then?'

'A bit. He was talking about there being no justice, not even in the law. He said rich newspapers could afford expensive lawyers so that poor men like him didn't stand a chance.' She laughed. 'He was that upset he overturned the glue-pot. But it was just his way, Mr Stafford.'

'Oh! What was he doing with the glue-pot?'

'Pasting something into that scrapbook of his. The one that had all the stuff in it about his father. He thought a lot of his father although I don't think he could have remembered him. Stands to reason, doesn't it? He was only a little boy when his father was killed.'

'Did he ever show you the scrapbook?'

'Oh yes; it was one of the first things he did when he came here eight years ago. That was the year after my late husband died. It was full of pictures cut out of newspapers and magazines. – all about his father. Lots of aeroplanes – the old-fashioned kind like they had in the First World War.'

'Biplanes?'

'Lots of wings,' she said vaguely. 'I don't know much about aeroplanes. They weren't like the jets we have now. He told me all about his father lots of times; about how he was some kind of hero. After a while I just stopped listening and let it pass over me head. He seemed to think his dad had been cheated or something.'

'Do you mind if I see his room? I'd like to have a look at that scrapbook.'

Her brow wrinkled. 'I don't mind you seeing the room but, come to think of it, I don't think the book's there. It stays on his dressing-table and I didn't see it when I cleaned up.'

'I'd still like to see the room.'

It was not much of a place for a man to live. Not uncomfortable but decidedly bleak. The furniture was Edwardian oversize or 1930s angular and the carpet was clean but threadbare. I sat on the bed and the springs protested. As I looked at the garish reproduction of Holman Hunt's 'The Light of the World' I wondered why an?8000-a-year man should live in a dump like this. 'The scrapbook,' I said.

'It's gone. He must have taken it with him.'

'Is anything else missing?'

'He took his razor and shaving brush,' said Mrs Harrison. 'And his toothbrush. A couple of clean shirts and some socks and other things. Not more than would fill a small suitcase. The p olice made a list.'

'Do the police know about the scrapbook,'

'It never entered me head.' She was suddenly nervous. 'Do you think I should tell them, sir?'

'Don't worry,' I said. 'I'll tell them.'

'I do hope you can find Mr Billson, sir,' she said, and hesitated. 'I wouldn't want to think he's come to any harm. He really should be married with someone to look after him. His sister came every month but that really wasn't enough.'

'He has a sister?'

'Not a real sister – a half-sister, I think. The name's different and she's not married. A funny foreign name it is – I never can remember it. She comes and keeps him company in the evening about twice a month.'

'Does she know he's gone?'

'I don't know how she can, unless the police told her. I don't know her address but she lives in London.'

'I'll ask them,' I said. 'Did Mr Billson have any girlfriends?'

'Oh no, sir.' She shook her head. 'The problem is, you see, who'd want to marry him? Not that there's anything wrong with him,' she added hastily. 'But he just didn't seem to appeal to the ladies, sir.'

As I walked to the police station I turned that one over. It seemed very much like an epitaph.

Sergeant Kaye was not too perturbed. 'For a man to take it into his head to walk away isn't an offence,' he said. 'If he was a child of six it would be different and we'd be pulling out all the stops, but Billson is a grown man.' He groped for an analogy. 'It's as if you were to say that you feel sorry for him because he's an orphan, if you take my meaning.'

'He may be a grown man,' I said. 'But from what I hear he may not be all there.'

'I don't know,' said Kaye. 'He held down a good job at Franklin Engineering for good pay. It takes more than a halfwit to do that. And he took good care of his money before he walked out and when he walked out'

Tell me more.'

'Well, he saved a lot. He kept his current account steady at about the level of a month's salary and he had nearly?12,000 on deposit. He cleared the lot out last Tuesday morning as soon as the bank opened.'

'Well, I'm damned! But wait a minute, Sergeant; it needs seven days' notice to withdraw deposits.'

Kaye smiled. 'Not if you've been a good, undemanding customer for a dozen or more years and then suddenly put the arm on your bank manager.' He unsealed the founts of his wisdom. 'Men walk out on things for a lot of reasons. Some want to get away from a woman and some are running towards one. Some get plain tired of the way they're living and just cut out without any fuss. If we had to put on a full scale investigation every time it happened we'd have our hands full of nothing else, and the yobbos we're supposed to be hammering would be laughing fit to bust. It isn't as though he's committed an offence, is it?'

'I wouldn't know. What does the Special Branch say?'

'The cloak-and-dagger boys?' Kaye's voice was tinged with contempt. 'They reckon he's clean – and I reckon they're right.'

'I suppose you've checked the hospitals.'

Those in the area. That's routine.'

'He has a sister – does she know?'

'A half-sister,' he said. 'She was here last week. She seemed a level-headed woman – she didn't create all that much fuss.'

'I'd be glad of her address.'

He scribbled on a note-pad and tore off the sheet. As I put it into my wallet I said, -And you won't forget the scrap-book?'

'I'll put it in the file,' said Kaye patiently. I could see he didn't attach much significance to it.

I had a late lunch and then phoned Joyce at the office. 'I won't be coming in,' I said. 'Is there anything I ought to know?'

'Mrs Stafford asked me to tell you she won't be in this evening.' Joyce's voice was suspiciously cool and even.