The Long Earth

frosty world some way back have had the same idea.’
    ‘The trolls? What do you mean?’
    ‘I’ve been observing scattered bands of them, travelling across the worlds. Trolls, and what appear to be other related species, of variant forms. It’s difficult to tell in our brief glimpses; there is much to be studied. But simple demographic tracking suggests that on the whole they are heading
back
along the line of our journey, quite a number of them, too. Possibly some kind of migration.’
    ‘Hmm,’ Joshua said, feeling that faint pressure in his head. ‘Or maybe they’re fleeing something.’
    ‘Either way, it’s interesting, don’t you think? Stepping humanoids! And I wonder what will happen when more of the migrant trolls reach the Datum itself.’
    ‘
More
of them? What do you mean by that?’
    ‘I’ve told you of fragmentary reports from old traditions – glimpses of transitory beings, tales from myth. I believe that trolls and other species have been visiting our Earth for millennia – perhaps simply to pass through, perhaps for other purposes. The frequency of such reports drops in recent centuries, because of the growth of scientific literacy perhaps.’
    Or sheer mental pressure, Joshua thought, as the Earth’s population grew, if the trolls and their cousins had the same reaction to crowds as he had.
    ‘But in recent decades, and even since Step Day, such sightings have been on the increase again. The wavefront of the migration we are witnessing, perhaps. Let me give you an example, of a case that now makes a certain kind of sense …’

27
    ACCORDING TO THE report filed by the two students later – filed and briskly covered up under Britain’s Official Secrets Act – the night of the incident had been cloudy, the sky black. This was darkest Oxfordshire, the very centre of England. By the light of their battery-powered storm lantern Gareth unpacked his canvas rucksack and set out the instruments: a cricket bat and stump, a baseball bat, drumsticks filched from the college orchestra’s percussion section, even a croquet mallet. Stuff to hit the standing stones with.
    While Lol was thumping his forehead against an oak tree.
    The oak, with its fellows, towered over the stones, which were like a ring of broken giants’ teeth stuck in the ground. This was said to be one of the oldest monuments in the country – possibly it even pre-dated the age of the farmers who had produced most of the great stone monuments in Britain. But nobody knew for sure, because there’d been no decent archaeological investigation of the site. There was no nicely laid footpath, no information trail with boards of factoids to guide the visitors who never came. Just the stones, and the forest that had all but overwhelmed them – and a legend, that these stones would sing, to keep elves and other demons out of the world. A legend that had brought Gareth here in the first place.
    Lol wrapped his arms around the tree’s gnarly trunk. ‘Trees! Trees root us, Gaz. They nurture us. There have been trees on this planet for three hundred million years. Did you know that? Great huge tree ferns back in the Carboniferous. A tree is defined by its form, not by its species. Once we
lived
in trees. Trees are at the centre of all our myths! There are stories from all over of world trees, like ladders to the sky.’
    They were both science students, twenty-year-old undergraduates, Lol studying quantum physics, Gareth acoustics. Lol looked younger than his age, like a fifteen-year-old in biker fancy dress, and he did live at home with his parents. But for all the green mythology stuff he liked to spout, you had to remind yourself that Lol had a sharp mind. Gareth found the nonlinear equations of fluid mechanics that underlay the acoustics he studied pretty challenging, but Lol’s quantum physics was
hard
…
    Gareth heard a pop, like somebody stepping. He turned. He thought he glimpsed movement in the long shadows the stones cast in the lantern light. Some forest creature out foraging?
    Lol said now, ‘Give me a beer.’
    Gareth stared at him. ‘You were bringing the beers.’
    ‘
You
were.’
    ‘I brought the mallets. Christ. You never do buy your round.’ He threw a kettledrum stick, narrowly missing Lol’s head. ‘If we’ve got no ale let’s get this over with, and get back to the pub before we sober up.’
    ‘Sorry, man.’ Lol picked up the drumstick.
    Gareth dug out his phone and set it to record the sounds