‘My mother’s dead. She died in a car accident when I was ten. She never told anyone who my father was – not even Phil.’

‘Phil?’ I couldn’t think of how to indicate a question mark, and decided to drop the game temporarily. This was no time for experimentation.

‘My’ – hands up, fingers wiggled – ‘father. Who’d go ape-shit if I told him I wanted to know.’

Rosie drank the remaining wine in her glass and refilled it. The second half-bottle was now empty. Her story was sad, but not uncommon. Although my parents continued to make routine, ritual contact, it was my assessment that they had lost interest in me some years ago. Their duty had been completed when I was able to support myself. Her situation was somewhat different, however, as it involved a stepfather. I offered a genetic interpretation.

‘His behaviour is completely predictable. You don’t have his genes. Male lions kill the cubs from previous matings when they take over a pride.’

‘Thanks for that information.’

‘I can recommend some further reading if you are interested. You seem quite intelligent for a barmaid.’

‘The compliments just keep on coming.’

It seemed I was doing well, and I allowed myself a moment of satisfaction, which I shared with Rosie.

‘Excellent. I’m not proficient at dating. There are so many rules to remember.’

‘You’re doing okay,’ she said. ‘Except for staring at my boobs.’

This was disappointing feedback. Rosie’s dress was quite revealing, but I had been working hard to maintain eye contact.

‘I was just examining your pendant,’ I said. ‘It’s extremely interesting.’

Rosie immediately covered it with her hand. ‘What’s on it?’

‘An image of Isis with an inscription: Sum omnia quae fuerunt suntque eruntque ego. “I am all that has been, is and will be.” ’ I hoped I had read the Latin correctly; the writing was very small.

Rosie seemed impressed. ‘What about the pendant I had on this morning?’

‘Dagger with three small red stones and four white ones.’

Rosie finished her wine. She seemed to be thinking about something. It turned out not to be anything profound.

‘Want to get another bottle?’

I was a little stunned. We had already drunk the recommended maximum amount. On the other hand, she smoked, so obviously she had a careless attitude to health.

‘You want more alcohol?’

‘Correct,’ she said, in an odd voice. She may have been mimicking me.

I went to the kitchen to select another bottle, deciding to reduce the next day’s alcohol intake to compensate. Then I saw the clock: 11.40 p.m. I picked up the phone and ordered a taxi. With any luck it would arrive before the after-midnight tariff commenced. I opened a half-bottle of shiraz to drink while we waited.

Rosie wanted to continue the conversation about her biological father.

‘Do you think there might be some sort of genetic motivation? That it’s built into us to want to know who our parents are?’

‘It’s critical for parents to be able to recognise their own children. So they can protect the carriers of their genes. Small children need to be able to locate their parents to get that protection.’

‘Maybe it’s some sort of carry-over from that.’

‘It seems unlikely. But possible. Our behaviour is strongly affected by instinct.’

‘So you said. Whatever it is, it eats me up. Messes with my head.’

‘Why don’t you ask the candidates?’

‘ “Dear Doctor. Are you my father?” I don’t think so.’

An obvious thought occurred to me, obvious because I am a geneticist.

‘Your hair is a very unusual colour. Possibly –’

She laughed. ‘There aren’t any genes for this shade of red.’

She must have seen that I was confused.

‘This colour only comes out of a bottle.’

I realised what she was saying. She had deliberately dyed her hair an unnaturally bright colour. Incredible. It hadn’t even occurred to me to include hair dyeing on the questionnaire. I made a mental note to do so.

The doorbell buzzed. I had not mentioned the taxi to her, so brought her up to date with my plan. She quickly finished her wine, then stuck her hand out and it seemed to me that I was not the only one feeling awkward.

‘Well,’ she said, ‘it’s been an evening. Have a good life.’

It was a non-standard way of saying goodnight. I thought it safer to stick with convention.

‘Goodnight. I’ve really enjoyed this evening.’ I added, ‘Good luck finding your father’ to the formula.

‘Thanks.’

Then she left.

I was agitated, but not in a bad way. It was more a case of sensory overload. I was pleased to find some wine left in the bottle. I poured it into my glass and phoned Gene. Claudia answered and I dispensed with pleasantries.

‘I need to speak with Gene.’

‘He’s not home,’ said Claudia. She sounded disoriented. Perhaps she had been drinking. ‘I thought he was having lobster with you.’

‘Gene sent me the world’s most incompatible woman. A barmaid. Late, vegetarian, disorganised, irrational, unhealthy, smoker – smoker! – psychological problems, can’t cook, mathematically incompetent, unnatural hair colour. I presume he was making a joke.’