‘All right, it was me,’ he said unhappily. ‘They were coppers. I didn’t want them blundering in on the op. They weren’t pleased about me warning them off, but I told them if there was a leak or anyone worked out who they were, the chief inspector would have their guts for garters. I’m sorry about the lie, Tilly, but I thought it necessary at the time. If it had happened today I’d have told you straight off.’

Strangely, she believed him. ‘Was it because you didn’t trust them personally, or . . .?’

He shrugged. ‘They were straight enough, as far as I know, but cops are like anyone else. They talk about stuff, about ops that are running, and it could get to the wrong ears. This one’s supposed to be watertight, on a strict need-to-know basis. I rang the inspector straight after they left – he’ll have had a word with them, so hopefully they’ve kept their mouths shut. One of them was actually from the op, so he’s solid. He was showing initiative, I guess.’ He was gazing ahead at the spread of vivid green bush. ‘Hmm, pretty big area by the looks of it. A lot of water then?’

‘Tons of it. Coming straight out of the cliff face. Luke says it dries back to a trickle but never actually stops flowing, even late in the year. The ground’s quite boggy all around the perimeter. You have to walk in, starting from about where those anthills are.’

‘We might give it a miss for now, unless our quarry has stopped. Doesn’t seem to have though.’

‘No.’ The tracks ran straight on, following the rudimentary road as it curved south-west along the face of the escarpment, the height of which gradually decreased, running low to the horizon in a series of yellow and ochre hills bearing none of the grandeur of the cliffs along the Nutt River. The soil changed until they were driving on red gravel, which glittered in the sun. A family of wallabies broke from their camp beneath a wattle bush, and Tilly remembered what Matt has said about ticks. She reached to pull her socks over the legs of her jeans and then pointed at several dark hollows in the hills. ‘Is that them?’

‘Looks like it.’ Connor scanned the surrounding barren slopes and low scrub, then leant out his window to study the tracks. ‘They stopped here, and yep, headed for the caves. Then they’ve gone off over the ridge there. What’s out that way?’

‘I’ve no idea. A place they call the Lost City is somewhere behind the range, but why would they go there?’