'Shooting anyone special?' Louisa said, eyeing the gun which I was carrying with me.

'Didn't want to leave it unattended.'

'Is it loaded?' Her voice sounded almost hopeful. By late Friday, she was always in the state in which one never asked her for an extra favour: not, that is, unless one was willing to endure a weepy ten minutes of 'you don't realise how much this job entails', which, on most occasions, I wasn't. Louisa's tantrums, I reckoned, were based on her belief that life had cheated her, finding her at forty as a sort of store-keeper (efficient, meticulous and helpful) but not a Great Scientist. 'If I'd gone to college…' she would say, leaving the strong impression that if she had, Einstein would have been relegated. I dealt with Louisa by retreating at the warning signs of trouble, which was maybe weak, but I had to live with her professionally, and bouts of sullenness made her slow.

'My list for Monday!' I said, handing it to her.

She glanced disparagingly down it. 'Martin has ordered the oscilloscopes for third period.'

The school's shortage of oscilloscopes was a constant source of friction.

'See what you can manage,' I said.

'Can you make do with only two?'

I said I supposed so, smiled, hoped it would keep fine for her gardening, and left for home.

I drove slowly with the leaden feeling of resignation clamping down, as it always did on the return journey. Between Sarah and me there was no joy left; no springing love. Eight years of marriage, and nothing to feel but a growing boredom.

We had been unable to have children. Sarah had hoped for them, longed for them, pined for them. We'd been to every conceivable specialist and Sarah had had countless injections and pills and two operations. My own disappointment was bearable, though none the less deep. Hers had proved intractable and finally disabling in that she had gone into a state of permanent depression from which it seemed nothing could rescue her.