I shine a torch into the corners of the coop where O’s specials are kept. There were four, last I remember; now there are only three.

‘One of them is gone. I wonder when she did that.’

‘You’re sure this happened recently?’ Roman asks.

‘The last couple of days I honestly didn’t count. I checked their water and I fed them, but I didn’t clean the cage or handle any of them, and I couldn’t swear to how many there were. I’ve been pretty distracted.’

‘Try to remember. Think, Charlie.’

‘I am thinking! I’m not the world’s most observant person. You know how when there’s a crime and the police say, What colour and make was the car? And people go, Oh yeah, it was a silver Fiat Punto. But I’m like, Hey, there was a car or maybe a plane or a train . . . I just don’t notice stuff like that.’

Roman shakes his head in disparagement.

‘I have a rich inner life,’ I add feebly.

‘You’re sure only one is missing?’

‘Yeah. I’m sure. She must have let it out the day she fell. I’ve been here since she went to hospital. Unless I was asleep . . .’

‘What about the rest of them?’

‘They’re all still in, waiting to be fed.’

‘The ones in the big coop aren’t necessarily homed here. Some I know for sure are homed to Daphne’s place as well as here, because I recognise them. The others, I’m not sure.’

‘So think about what you’ve seen her do. Does she get any of the non-Daphne ones to carry messages?’

I can feel my face making a curdling expression. ‘Maybe? I really don’t know, I never pay attention . . . I have narcolepsy . . .’ I yawn.

‘No, don’t get sleepy on me. Stay calm and think.’

‘Well, I can show you the equipment she uses for messages. Would that help?’

‘Yes.’

So I show him the little nylon pouches that attach to the birds’ legs with Velcro. They are paper-thin and flexible.

‘You could fit a drive in one of these pouches, easily,’ Roman says. ‘Does O have any other computers besides her main workstation?’

‘I don’t know and I’m not going to violate her privacy.’

‘OK, don’t get upset. Never mind what she uses the pouches for.’ He goes into the kitchen and sets up a workstation on the counter, pulling a security-sealed envelope out of his backpack and carefully unwrapping it. ‘I’m thinking to put the trackers in these pouches and then send out our scouts once we see where the birds are heading. I wonder if they fly after dark?’

‘It’s still morning – how far are we thinking they’ll need to go?’

‘That’s just it. We don’t know.’

‘Well, they can get to Dorking in a couple of hours.’