‘I was here in the ward, but not in the room with Marion. The day she died and the day before – Monday and Tuesday – I didn’t go into her room at all.’

‘Why not?’

‘I didn’t want to. I spent Saturday and Sunday in there, after which I decided I didn’t enjoy being in a room with a dying person. It’s a more unpleasant experience than you’d think, believe me.’

‘So where were you Monday and Tuesday?’

‘Sitting in the corridor.’

‘Where exactly, in relation to Marion’s room?’ asks Waterhouse.

‘About three feet to the right of the door.’

‘That’s easily close enough to see who goes in and out.’

‘It is if I’m looking. Mainly, I wasn’t. I was fiddling with my phone a lot of the time – Googling what happens if you swallow a ringpull.’

‘A ringpull?’ Waterhouse glances at Gibbs. ‘From a can?’

‘Yeah. I’d accidentally washed one down with Fruit Rush and I was trying to find out if I could risk doing nothing about it. I was also answering emails, reading Twitter – anything I could to distract me from Marion dying. I was aware of nurses going in and out of her room all the time; after a while I stopped paying attention. It annoyed me too much. They’d refused to catheterise her in case it gave her a bladder infection – obviously those are hugely annoying to dead people – and they refused to put an end to her misery, so I tuned out and focused on my little screen.’

‘Could someone who wasn’t wearing hospital clothing have gone in without you noticing?’

‘Seventeen people wearing “I’m a serial murderer” leotards could have gone in and I’d have been none the wiser. This is what I’m trying to tell you.’

Waterhouse sighs.

‘What about the ward itself?’ asks Gibbs. ‘Surely those seventeen people wouldn’t have been buzzed in.’

‘Don’t count on it,’ I tell him. ‘When I went back to the ward to get Billy’s white book, they buzzed me in without seeing my face or hearing my voice.’

‘Great.’ Waterhouse sounds despondent. ‘Well, you’re now one of a clear third pair. Not a pair of best friends, but a pair. Relatives this time.’

‘I didn’t even like Marion,’ I tell him. ‘And she went one better: she formally expelled me from her family – bullied my mother into giving me up for adoption. It’s almost as if we knew a serial killer would one day decide to kill pairs of people who had a close bond, and set about trying to get ourselves off the hook!’ I giggle. ‘Sorry. Making jokes is what I do – whatever the occasion.’