They finally found, out by an annex, an undistinguished lawn, with a high wall around it. A children’s mural still smiled from the building beside it. The grass had been allowed to grow tall. They saw weeds and odd rough ditches in the light of the fires and a single blazing lamp at the corner. A small sign on what turned out to be a weather station indicated that this had once been the site of –

‘The Blue Peter garden,’ said Ross.

Sefton recalled the presenters of that children’s magazine programme going out and doing nature items here from time to time. He put down his holdall, and from it took the spades and pickaxes they’d brought along – looted, frankly, from the smashed open window of a hardware store. The fury was now broadcasting from the ground right beneath him. He wouldn’t need a map to pinpoint it. They had no idea what they would find down there, knowing only that – in the absence of Mary Arthur – this was their only remaining hope. So he was going to fucking dig until it gave way or he did. He just hoped nobody wandered past and saw what they were doing. ‘If anyone asks,’ he said, sinking his spade into the ground hard and fast with his boot, ‘we’re looking for the tortoises, the time capsule and the skeleton of Petra.’

*   *   *

It took a lot of digging before the quality of the surface underneath their spades changed. They dug too fast, and their heads started swimming with the effort until what they were doing started to feel like a dream and they kept having to yell at each other to keep going. People did come past, but none of them saw fit to challenge what they were doing on this uncared-for land, not tonight.

They hit stone. Sefton grabbed a pickaxe and started working away at it, slamming and slamming and slamming the blade into the rock, and eventually there was a block that could be cracked away with a crowbar and lifted out. Muscles crying out, they prised it out to reveal a gap into darkness beneath that was big enough for a person to get through, just. Sefton waited, hanging over the edge, thinking that maybe his goal was complete. He’d half expected this moment to free some howling banshee, but no. The archaeological survey of this thing had reported an inner chamber that had remained sealed. Maybe it was in that. Whatever it was.

They looked into the dark.