Parry reads the words aloud – ‘ “Just YOU wait” ’ – before turning a baleful eye my way. ‘What does that mean, exactly?’

‘It was a response to what he’d said to me. He threatened me, said he knew people I had no idea existed. “Just you wait, Jamie”: that was the last thing he said to me, I swear to God. I sent that text because I had to show him I wasn’t intimidated. I had to get the last word.’

There’s an unwelcome sinister edge to this last phrase, given the context, but I can’t take it back.

‘What did he mean by people you had no idea existed?’

‘I assumed he meant criminals. His drug buddies, men he could ask to hurt me. He said they were animals.’

While Parry scans the previous messages between Kit and me, Merchison watches me with a certain scepticism. ‘Maybe “threaten” is too strong a word,’ I correct myself. ‘I’m not scared of Kit, it was more low-level harassment. But the reason I’m showing you is the timeline.’ I take the phone from Parry to remind myself. ‘I sent this when I got home. See the time? Eleven thirty-eight. The boat docks at eleven thirty. I was texting as I walked through the door, Clare can confirm I was home at that time.’

‘I’m not sure I understand your point,’ Parry says.

‘My point is, he’s opened it, see? It’s marked as read. Since he couldn’t have opened it before it was sent, he was obviously still alive and kicking after I got home.’

I wish I didn’t keep saying ‘obviously’; if I were a police officer, it would make me think a lie was being fed to me. ‘Then, at seven a.m., Clare and I got a taxi to Kings Cross for our train to Edinburgh. She’ll tell you we were on the eight-fifteen train together or, if you don’t believe her, check the station’s CCTV – and the train’s.’

Parry raps the nails of his right hand against the knuckles of his left. ‘You seem very confident of the cameras. Almost as if you’ve gone out of your way to be seen.’

I hold my nerve. ‘There’ve got to be some advantages to living in a surveillance state.’

‘So that was your last communication with Mr Roper. What about Mrs Roper? You said you hadn’t had a chance to return her calls: it’s quite a coincidence you were so distracted during the same period your friend went missing.’

I’ve been expecting this to come up. ‘I was at my partner’s parents’ house, so I was hardly likely to phone my secret girlfriend, was I? I mean, I saw she’d left voicemails, but I just assumed that she was, you know, on my case.’

‘About not being in contact over Christmas, you mean? The ignored mistress?’

‘Yes, if you want to put it like that. And since I didn’t know Kit was missing, it wasn’t much of a coincidence to me.’ If my gaze is firm, his is granite-hard. ‘Why don’t you get hold of his phone activity from Monday night and find out when he opened this text? Find out if he made any calls after that, talk to the people he phoned. It will help your timeline more than talking to me.’

Really, I’m the one who should be a detective here.

‘Thanks for the tips,’ Parry says. As the din of voices in the hall suddenly rises, his, almost capriciously, grows very quiet, causing me to lean in to hear. ‘Here’s a timeline for you, Jamie: you stalk off after this row on the boat and wait somewhere out of sight for when Kit walks by. You lure him to this blackspot you told us about, where you continue your argument. Things get out of hand and you kill him, maybe using something you took from your place of work, which I assume contains catering equipment. Sharp knives.’ There’s a significant pause. ‘Maybe you cut yourself while you’re at it.’

All three of us lower our eyes to my bandaged hand and I know what they’re thinking. If I really had just burned it, wouldn’t I unwrap the dressing and prove it? As if from the scrutiny, the wound begins to throb.

‘You take his phone, so you can open the text you’re going to send to him afterwards, to make it look like it’s been read by him, then you dispose of his body over the river wall,’ Parry finishes.

The pull of my breath is audible. ‘Over the river wall? You’re kidding, aren’t you? It’s pretty high – what am I, the world’s strongest man?’

‘He doesn’t weigh that much. Not even eleven stone. Any fitness expert would agree it could be done.’

Merchison watches his colleague with undisguised admiration. Whatever theory they came here with, Parry has developed it. A horrible notion occurs: what if I haven’t cleared myself with this eleventh-hour seizing of momentum, but helped him fill in the details that might incriminate me? What the hell have I done? ‘Prove it,’ I say, my voice returning to the growl of early morning, the animal protest at being singled out. ‘Prove that someone could do all that between when the boat docked at eleven thirty and when I was witnessed arriving home at eleven thirty-eight. Eight minutes! There’s no way, no way on earth. Check the cameras, how many more times do I have to say it?’ I stand, agitated. ‘I think it’s time I got a solicitor involved here. You can’t accuse me like this, it can’t possibly be legal. I’m not answering any more questions until I’ve taken advice.’

Merchison stands too, hands raised in appeal, gaze warm with fellow feeling. ‘No need for that, Jamie, we’re only thinking aloud. This is all completely informal, none of it is on record. And no one’s accusing you of anything. We’re grateful for your help, aren’t we, Ian?’

‘Absolutely.’ Nodding, even managing a smile, DC Parry taps his pen on the open page. ‘All we need now is for you to talk us through Monday evening and then we’re finished.’

I stare at him. Petty to glory in that rare smile, but I do. ‘Five more minutes,’ I say. And I sit back down.

25

December 2019

Now I think about it, maybe it was Gretchen who suggested our little festive celebration. ‘Do you realize we’ve never had a drink together when we haven’t had life jackets under our seats?’

‘Don’t forget Kit’s wedding,’ I said. ‘We were on terra firma then. How about the last day we’re all in work? When is that?’

All of us but Gretchen had booked Christmas Eve off work, which made Monday the 23rd the natural date and everyone plugged it into their calendars.

‘Are you bringing partners?’ Steve asked Kit and me, hopefully, and I hid a smirk. He must fancy Melia, just like Clare said he would.

‘No, don’t,’ Gretchen said, firmly.

In a strange – or perhaps inevitable – parallel to the breakdown in friendship between the Ropers and Clare and me, there was a strong sense that our days as a commuter quartet were numbered. Every morning now I looked forward to the short stretch of solitude after the others had left the boat. Through the red-and-gold arches of Blackfriars Bridge I’d go in glorious silence, past the north bank barges with their cranes and groaning construction machinery and, on the south, the tiny sandy beach and wooden piers so picturesquely exposed by the low tide; then on past the magnificent Brutalist National Theatre, without risk of reopening Kit’s thespian wounds about not being a contender. No, it seemed to me there was more to avoid now in my fellow commuters than there was to seek out, but I didn’t feel sad about it, not like I did about the loss of friendship between the Ropers and Clare and me. A time to weep and a time to laugh – we all know the line.