My mother was face down on the bed. I could see no sign of a struggle, but I remembered April – ‘I didn’t leave the door open, Lisa – it was already wide open’ – looking frightened in the hall. Did she know something about what happened here? Was my son here before me? Or was it just the fright . . .? Yes, of course, that’s all it was. It would be shocking to anyone, the discovery of their friend dead.

I stared at my mother’s body; she was fully clothed. She had jeans on, socks, and her favourite ivy-coloured cardigan that belts like a dressing gown. She always called it a housecoat and I knew what she meant – in colder months she would come in, take her real coat off, and put the long, thick cardigan straight on. I don’t think I’ve seen her wear anything else in the evening. She was never a wearer of ballgowns but if she were, then I think she would’ve just popped that over the top. It looked dreadful: tired and worn, a hole laddering one elbow, a dropped hem and a missing pocket all meant that it begged to be binned.

It was not fit to be seen by anyone except her very nearest and dearest.

My brain was sluggish with shock; it ruminated on this essential fact like it was important. It was that the housecoat screamed out to me, its tired, synthetic voice rising shrill above the silence of my mother’s bedroom.

It was its very ugliness that made it so important. My mother was not a vain woman, but she had her standards. She wouldn’t wear make-up, but she would always brush her hair if she knew someone she didn’t know was coming to the flat. And she most certainly, definitely wouldn’t wear her cardigan in front of even a delivery driver.

And yet she was wearing it now.

Whoever she let in, she knew well enough not to take her cardigan off for. Someone who had already been buzzed in from the front door.

I know it was him. I know it was her grandson. After I took Jack, he must’ve either come here first or gone straight to Sunningdale before coming here. She let him in and then . . .

Did I really believe that? My son, the arsonist murderer?

– The door was open wide –

I reached out, and with a butterfly touch my fingertips landed on her skin above her sock, below her rucked-up trousers. I had to know and the warmth of her body instantly told me what I didn’t want to understand – she was alive very, very recently. I didn’t need a pathologist’s graph of heat loss from a body – I’ve worked around more dead bodies than most after a career in elderly nursing, and certainly enough to know that my mother was alive within the last hour or so.