‘Oh yes, the virus optimizes survival, optimizes flesh growth: the leech’s harvest. This isn’t necessarily what’s best for humans, though. Flatworms are better survivors than us humans,’ she said.

‘Well, that’s nice to know,’ said Janer, thinking he really didn’t want to know any more. Erlin continued remorselessly as they followed the others away from the overnight camp.

‘The worst thing is when a human mind ends up in the body of a leech. That didn’t happen to Ambel, probably because he was fed upon too much to build up the energy to make that change; and when Sprage hauled him up out of the sea, he was fed Dome-grown food to prevent it. When the transformation does start to happen, and can’t be prevented, Hoopers feed the victim sprine. For all of them it’s their greatest fear: to end up being only able to feel vibration, heat, pain or hunger.’

‘Could there be many of them about?’ Janer asked, thinking with horror of the huge leech he’d burned during the night.

‘There could,’ said Erlin, offering no comfort.

As they stomped on, deeper into the dingle, Janer began to notice pronounced changes in the flora and fauna. The swollen trunks of the peartrunk trees were larger, and they often had large splits running through them, so that they seemed more like barred cages than solid trees. The leeches in their branches were dark red rather than the usual brown of coastal or seagoing leeches, and here the frogmoles were absent. After a time, Ambel no longer needed to use Ron’s machete, as the growth of foliage became steadily higher. The large flat leaves that grew at ground level near the coast now sprouted at the top of thorny trunks standing five metres tall. It was dark here and the ground was coated with soggy rolls of leaf and brittle white twigs. Fungi were scattered amidst this like droplets of orange blood. Now the leeches falling from above were not their worst problem; it was the leeches lurking in the fallen foliage that oozed towards one’s ankle if standing in one spot for too long.

When Ambel suddenly called a halt, Janer thought this a foolish place to choose, until he realized they were pausing only to allow another denizen of the dingle to pass.