‘We don’t know if they killed them or if they were dead already,’ says Max calmly, ‘but the bodies are often children’s’.

‘Jesus.’

They have reached the trench which has been covered by a blue tarpaulin. Ruth peels back the covering and kneels on the edge of the trench. Nelson crouches beside her. He sees a neat, rectangular hole (he often wishes that his crime-scene boys were as tidy as archaeologists), the edges sharp and straight. The trench is about a metre deep and Nelson can see a clear cross-section of the layers as the topsoil gives way to clay and then chalk. Below the chalk, a line of grey stones can be seen. Next to the stones a deeper hole has been dug. At the bottom of this hole is a gleam of white.

‘Haven’t you dug them up?’ asks Nelson.

‘No,’ says Ruth, ‘we need to record and draw the grave and skeleton on plan so that we can understand its context. It’ll be really important to check which way the skeleton is lying. Could be significant if it points to the east, for example.’

‘The brothers used to tell us to sleep with our feet to the east,’ says Nelson suddenly remembering, ‘so that if we died in the night we could walk to heaven.’

‘An interesting survival of superstition,’ says Ruth coolly. Nelson remembers that she has no time for religion. ‘Churches,’ Ruth goes on, ‘are nearly always built east to west, never north to south.’

‘I’ll remember that.’

‘And sometimes,’ cuts in Max, ‘men are buried facing west and women facing east.’

‘Sounds sexist to me,’ says Nelson straightening up.

‘And you’re never sexist,’ says Ruth.

‘Never. I’ve just been on a course all about redefining gender roles in the police force.’

‘What was it like?’

‘Crap. I left at lunchtime.’

Ruth laughs and Max, who has been looking disapproving, smiles too, looking from Ruth to Nelson and back again. Clearly more is going on here than he realised.