‘Is that what we are to you?’ Gwen asked. ‘Children?’

‘That’s all we are,’ he replied. ‘To them.’

‘And who are They?’

‘Who are They? They are the ones who live over the walls of the garden, in the wilderness outside. Me — I’m just a child as well, playing in the garden with the rest of you. The difference is, I’m just a little older. And I’ve already had my share of poison ivy rashes.’

Gwen gazed around at the top of the building, at the grasses and the weeds that occupied the spaces between the ventilation ducts and antennae, swaying gently in the evening breeze. ‘Life survives, doesn’t it?’ she said, apropos of nothing. ‘Finding little nooks and crannies to grow in. Putting down roots where it can, eking out some kind of existence in the cracks.’

‘And that’s what we do.’ The wind caught his coat, billowing it out behind him, but he seemed oblivious to the possibility of being blown off the building. ‘In Torchwood. We look for the things that have been blown in on the breeze between the worlds, and if necessary we eradicate them.’

Caught by a sudden premonition, Gwen looked at her watch. ‘Jesus! I’ve got a dinner appointment.’ She’d arranged to meet Rhys in a restaurant nearby — an apology of sorts for the amount of time she seemed to be spending away from him at the moment. Time she was spending with Jack. She turned to leave, then turned back, curiously unwilling to leave. ‘Are you coming down at all tonight, or are you going to stay here until dawn?’ she asked.

‘I’ll see how the mood takes me. How about you? Want to give dinner a miss and come join me on the edge?’

‘Thanks, but no. Gotta go.’

‘Just out of interest, why did you come up here in the first place?’