I wasn’t best pleased because Sunday is one of the few days I don’t have morning practice on the firing range and I was planning a nice lie-in followed by football in the pub.

‘So where’s this ghost?’ I asked when Abigail opened her front door.

‘How come there’s two of you?’ asked Abigail. She was a short skinny mixed-race girl with light skin that had gone winter sallow.

‘This is my colleague Lesley May,’ I said.

Abigail stared suspiciously at Lesley. ‘Why are you wearing a mask?’ she asked.

‘Because my face fell off,’ said Lesley.

Abigail considered this for a moment and then nodded. ‘Okay,’ she said.

‘So where is it?’ I asked.

‘It’s a he,’ said Abigail. ‘He’s up at the school.’

‘Come on then,’ I said.

‘What, now?’ she said. ‘But it’s freezing.’

‘We know,’ I said. It was one of those dull grey winter days with the sort of sinister cold wind that keeps on finding ways through the gaps in your clothes. ‘You coming or not?’

She gave me the patented stare of the belligerent thirteen-year-old but I wasn’t her mother or a teacher. I didn’t want her to do something, I wanted to go home and watch the football.

‘Suit yourself,’ I said and turned away.

‘Wait up,’ she said. ‘I’m coming.’

I turned back in time for the door to be slammed in my face.

‘She didn’t invite us in,’ said Lesley. Not being invited in is one of the boxes on the ‘suspicious behaviour’ bingo form that every copper carries around in their head along with ‘stupidly overpowerful dog’ and being too fast to supply an alibi. Fill all the boxes and you too could win an all-expenses-paid visit to your local police station.

‘It’s Sunday morning,’ I said. ‘Her dad’s probably still in bed.’

We decided to wait for Abigail downstairs in the car where we passed the time by rooting through the various stake-out supply bags that had accumulated over the year. We found a whole tube of fruit pastels and Lesley had just made me look away so she could lift her mask to eat one when Abigail tapped on the window.