‘Yes. I followed where I thought it came from, all the way down here to this bullseye arch, but now, I don’t know. He’s not here. I went wrong somewhere. And I tripped on something, when I climbed the other side of the wall, and now my ankle is shot. God knows where my cane is.’

‘You’re a bloody idiot!’ I cry and my voice ricochets up the vast, never-ending chamber of the reservoir. I feel around for the cane but I can’t find it. ‘You could have done so much worse! You came down all those steps and you walked all the way down here! What on earth were you thinking? You could have gone back into the park, or into the fair, and asked for help! Done something sensible. You’re not some kind of superhero, Dad! And just because you’ve been to the Albert Hall and the sodding Shard doesn’t make you some kind of blind bloody Christopher Columbus!’

‘Not a good analogy,’ says Dad calmly. ‘He went everywhere by ship.’

‘Well, maybe so should you! Honestly, Dad!’

‘Well, mi dispiace,’ says Dad, and I bet he is doing a typically Italian shrug. ‘I’m sorry. But Kemp needs our help and I have no idea where he is.’

We listen, in the dark, but there is silence, just the drip drip of water – like the ticking of a clock – and a scuttling sound. A rat? No, the rats are above us – those boys in the vests; the gits who plunged me into complete darkness. We listen again. And again. Eventually there is a low moan, from somewhere ahead of us.

‘The other side,’ Dad says. ‘I came to the wrong side.’

‘Kemp?’ I call out. ‘Is that you? Are you all right?’ There is no reply apart from another low moan. I start to feel my way to the low wall. I climb over it and land in the pool of water. I wade carefully in the cold and the pitch dark until I can feel the threshold of the eyelet the other side. There’s another moan, very close to me now.

‘Kemp, are you OK?’