They went past the gateposts at the end of the drive and Hannah smiled at the address carved into the stonework, 0 Greenhill Gardens. Number zero, just one of the things that marked this place as special. She asked Dorothy and Jenny about it when she was younger, but Gran just shook her head as if it was a cosmic joke, and Jenny shrugged like it never occurred to her that it was odd. Hannah did some research and it turned out their house was added to the street later than others, by an eccentric brewery owner in the late 1800s. In those days you could make up your own address, but instead of creating a new street name Mr Bartholomew plumped for number zero on the street already there, right next to the existing number one. Posties had been confused ever since.

Something about it appealed to Hannah’s mind. Zero was hard to define mathematically and asking about it led into philosophical 15territory, which she loved. She was studying metaphysics as an optional course, and sometimes popped into lectures on category theory, the maths of maths, to get her brain fried. That abstract space, the way matrices, theories and equations interlinked, the way they mapped out a universe you could superimpose on the real world, she was into it.

‘What are you smiling about?’ Indy said.

They were round the corner and into the park. The web of paths was full of students and workies heading home after lectures and the office. Hannah loved that everyone lived cheek by jowl here, she felt part of something.

‘Just happy to be alive,’ she said.

‘Oh my God.’

‘Which one?’

A running joke, Indy a lapsed Hindu.

The truth was Hannah really was happy to be alive, despite just watching her grandpa being cremated. Maybe because of that. Dorothy once told her that some people got horny at funerals, determined to get on with the business of living in the face of death. Hannah could relate.

They crossed Whitehouse Loan onto the north part of Bruntsfield Links where the pitch and putt was. The undulations of the ground always made Hannah think of the ancient burial site under the surface. She wondered how many of the kids and parents knocking golf balls around realised there were hundreds of seventeenth-century plague victims buried below. Another layer of existence beneath reality.