Upstairs, exactly two minutes later, the phone goes again, the sea shanty louder now and easily identifiable as coming from the doorway right ahead of me. I don’t dare open the door yet: it might make the ringtone loud enough for Jarrow to hear it downstairs and come looking for it.

I’m feeling a calmness that is unusual as I wait for it to ring out, then open the door. The room’s light is on, but the screen of the phone is still glowing from having rung. It’s right ahead of me on the desk, and I stride forward and almost scream when a huge swivel chair spins round and Jarrow, in an oversized onesie with a zebra pattern on it, leaps to her feet. She takes off her headphones in the same action as reaching for the phone and turning it on with her passcode.

She looks quizzically at the screen for a few seconds and sees that it shows ‘number withheld’ (at least, it should, if Boydy’s done it right), puts the phone down and gets back in her swivel chair, picks up her laptop, and spins round again, so her back is towards me.

This is a huge opportunity. The smartphone is unlocked, and will stay that way until it locks itself, usually after about half a minute of not being touched.

All I need to do is cross the room to the desk and touch the screen to stop it locking itself, then I can access all Jarrow’s phone data.

Four steps, I reckon. Five, maybe.

I’m going too slowly. At three steps, there’s a creaky floorboard and I don’t know for certain if Jarrow’s headphones are back on: the back of the chair is too high. And now I can’t wait any longer: the screen goes half dark, preparing to shut down. I take one big step, the floorboard creaks, and the minute I touch the screen to reactivate it, the chair swivels round again.

‘Jez?’ she says.

She must have heard something. I stand stiller than I have ever stood in my life, holding my breath until she swivels back – but only halfway.

She can’t see me, obviously. But she will see the screen on her phone changing if I do anything. She’s not looking at it, but it will attract her attention.

All I can do is stand there. I’m about a metre away from her, and my finger is hovering over the phone, preventing it from shutting down by touching it now and then, and I’m watching Jarrow very carefully in case she makes a sudden move in my direction.

Any calmness I had begun to feel has melted away and I’m so tense I swear you could twang me like a guitar string.

This goes on for nine whole minutes. I know because there’s a clock on the front of Jarrow’s phone showing the advancing time. Eventually, just as a cramp that started in my left foot is spreading up my leg, Jarrow sighs. She snaps shut her laptop, removes her headphones and stands up. She’s about to reach out for her phone so I take my hand away, but then she changes her mind and leaves it on the desk.

The minute she is out of the door, I’ve flipped open her laptop, and if I weren’t so nervous, I’d probably do a little jig of joy because it springs to life again, meaning I won’t need a password to access her stuff.

Result. Yay. Brilliant. Etc.

Now, get on with it, Ethel.

I’ve got her phone in my hands, and I’m scrolling through and trying to find where she might have the film of me.

It’s not a model I’m familiar with. I’ve got Gram’s old iPhone and I can find my way round one of them easily. This one’s an Android phone, and not even a well-known Android phone. Most of the app icons are the same, though, and I quickly work out where the movie clips are.

And there it is! The one taken in the school theatre has been sent to her on a clip-sharing app, and it’s easiest to delete the entire app and its contents. The whole film, including the security footage and the close-ups, is in a ‘Videos’ app, and that gets sent straight to the bin.

There’s a ‘deleted’ file in ‘Settings’. Empty that … click.

I search her emails for video attachments. Nothing.

Now for her laptop. That’s an Apple Mac, so it’s iMovies. Nothing there: the film wasn’t made on this then.

Emails: there it is! Sent two days ago. Click, gone.

iTunes: there it is again, saved from the email. Click, gone.

OK, OK, where else could it be?

Could there be a copy in a video player? I don’t know, but I open up QuickTime just in case: nothing there. Good.

Next, I search the whole laptop with the ‘search’ tool. Nothing. Even better.

Finally, empty ‘trash’.

I can hear footsteps on the stairs, and Jarrow saying, ‘Night, Jez! Night, Daddy!’ Her voice sounds different to normal: softer, and much less Geordie.

(Daddy? Jarrow Knight does not strike me as the kind of girl to call her father ‘Daddy’. In Jarrow’s normal accent, ‘Dad’ would be right, maybe even ‘Da’, but ‘Daddy’?)

Oh, Jarrow, I think. Why do you choose tonight to have an early night?

How do you empty the ‘trash’? I’m pressing buttons frantically, and the progress bar is telling me there’s loads of trash to delete, and it’s taking for ever, and I tell you this: I have no idea at all how Jarrow Knight did not see her laptop mysteriously closing itself as she came back into the room, or for that matter hear an anxious panting …

But I’ve done it.

Well … one part of it anyway.

I’ve got Jesmond’s to do next. Then I still need to check the family computer, if there is one. And deal with a huge, badly trained dog.

Oh, whoopee.