‘That may be true,’ Hemingway said. ‘Maybe they physically can’t look upwards. Why would they need to? Or maybe they just can’t process us, visually; we’re just too strange, like clouds come down to the ground . . .’

‘You mentioned “civilization”. I see a lot of rafts and fishers. What civilization?’

He straightened up. ‘Just over the dunes, Captain.’

The city of the crabs centred on what Gerry Hemingway believed was a temple complex. Or maybe it was a palace.

A big blocky building with open porticoes faced a long, wide rectangular pool, brimming with murky green water. What appeared to be a sculpture of a crab – like the raft pilots, but big, half the size of an adult human – loomed over the ‘temple’. Smaller sculptures, of crabs with upraised pincers, stood in a line around the pool, but Maggie thought that these life-size copies looked more like corpses, or maybe cast-off shells.

This complex, of pool and palace, was lined on all sides by more buildings, all more or less rectangular in form, but with softened edges, and all constructed of some hard, brownish substance. The palace, in fact, was the centrepiece of a straight-line grid-pattern of streets, which delineated blocks cluttered with buildings. The canal from the sea led straight into one big area that looked like warehousing, where, Maggie supposed, the incoming food was processed through in one direction, and the sewage bundled up and flushed away in the other. It was a regular city, and laid out in a surprisingly human-like fashion – unlike the irregular beagle city. But all the streets swarmed with crabs, scuttling this way and that. There were no vehicles on the land, but Maggie did see some of the smaller crabs riding on the backs of their bigger cousins.

And Maggie could step over the tallest buildings, like Gulliver in Lilliput. Where she planted her feet – with great care – in streets and open areas, the crabs still didn’t seem to perceive her properly; they just scuttled sideways around her big boots.

When she looked up she saw the comforting bulks of the twains, like a reminder of reality.

‘My God,’ she said to Hemingway. ‘It’s like a model layout. I keep expecting some toy steam train to come rattling around the bend.’

Hemingway seemed to be bursting to explain it all to her. ‘Here’s as much as we have figured out, Captain. We’ve been watching for twenty-four hours now. We think these ones—’ He bent down and pointed to a sample.

‘The raft pilots?’

‘Yeah. They are the smart ones. They’re males, who seem to dominate here. These others, the bigger ones, are the females for this species – many crab species have sexual dimorphism. Umm, they also seem to be using other species as draught animals, food stock maybe, construction workers. They don’t seem to have discovered the wheel – see, they ride the dumber ones?

‘The buildings are made of a kind of paste, of chewed-up shell and spit; they have a particular kind of animal that specializes in producing that. You can see there’s a big food processing area over there. We can’t even guess at the function of the rest of the buildings, the districts, though some are probably residential. On the Datum, crabs like to live in hollows, in caves, even in pits they dig out of the seabed . . .’

Maggie bent to look closer at the stationary crab likenesses around the pool. ‘Crabs moult, don’t they?’

‘They do, Captain. They cast off their outer shells regularly. And maybe that’s what this is. Not sculptures, like the big guy over the palace, but moulted shells discarded by – who? The emperor, his ancestors, a line of priests? And it is a him, you can see by the size of the shell. And kept for ceremonial purposes here.’

‘Lots of guesswork going on here, Gerry.’

‘Yes, Captain.’

‘Mo-hrre coming,’ said Snowy, and he stepped out of the way of the big thoroughfare that led up to the pool.

Here came a regular procession, a whole line of crabs heading for the central complex, most of them raft-pilot size but a few others in there too. Some seemed to have their shells decorated, red, black, purple, maybe with some relative of squid ink, Maggie thought. Others walking alongside clacked their pincers loudly in the air. Conversely there were others, in the middle of the crush, who looked kind of bedraggled, their shells scuffed and scarred. Some even had their pincers missing, nipped off at the joint, perhaps.

The only sounds were the clatter of pincers and the scraping of thousands of shells, a noise like sand on a window.

‘Soldier-hhrs with fallen en-hhemies,’ Snowy said, sounding almost sad. ‘Thei-hrr weapons-ss cut away.’

‘Perhaps. The kind of sight we’ve seen enough of on the Datum, in the past.’

Hemingway said, ‘Maybe those guys playing castanet aren’t making noises at random. Some crab species communicate with noises like that. On the Datum the message is usually just “That food is mine”, but here it must be more complex.’

Maggie said, ‘I wonder what fate awaits these prisoners when they reach that pool . . .’

‘Something’s happening at the palace,’ Hemingway said now. ‘Some kind of party coming out.’ He snapped at his team, ‘Make sure you record every damn moment of this.’

‘Yes, sir.’

Maggie bent down to see who was emerging from the spit-and-shell palace. One big crab in the centre of the party was surely the centrepiece of it all. His shell wasn’t marked, but he looked heavy, older, even indefinably arrogant to Maggie. He was surrounded by a circle of odd-looking acolytes, pink, vulnerable-looking . . . ‘My God,’ she said. ‘They have no shells.’

Hemingway said, ‘Maybe they’ve just moulted. When it moults the whole crab has to climb out of its old shell . . . Of course these companions look the right size to be females. In some crab species the females are mated just after moulting, when they’re softer. Hmm. I wonder if this emperor has some way to keep his harem from forming new shells. Thus keeping them sexually available for whenever he feels the urge.’

‘Ouch,’ Maggie said.

‘Yes, Captain. The procession is reaching the water.’

In the end the fate of the captives was brutal and decisive. One by one they were hurled into the pool, by the adorned soldier types. When the first captive hit the water the pool turned into a frenzy of activity, and was soon a mess of fragments of flesh and shell, and thrashing, struggling victims.

All the captives were thrown in, one by one, with horrible regularity, while the ‘emperor’ and his consorts looked on.

Hemingway said, ‘I wonder what they keep in that pool. Some kind of piranha?’

Snowy said, ‘Babies-ss.’

‘What?’

‘Babies. C-hhrab babies are let out by mother-hrr into water. Swim-mm. Find food. Not like pups, not-tt suckle.’

‘Ah,’ said Hemingway. ‘And in that pool—’

‘Babies of rule-hrr of this place. Eat enemy. Make babies-ss st-hrrong. Make them-mm fight each othe-hrr. Happens like this with us-ss. Pups tear-hhr apart fallen enemies-ss of mother-hrr.’

Hemingway and Maggie shared a glance. ‘You know,’ said Hemingway, ‘I bet you’re right. I never would have thought of it that way. It makes sense – a cultural logic deriving from the imperative of their biology.’

Snowy had to get that translated into simpler terms. But then he faced Maggie. ‘Your thought, my thought-tt, always at mer-hhrcy of blood, of body. Need other blood, other bodies, to p-hhrove thought. My blood not you-hhrs. My thought not you-hhrs.’

Maggie grinned. ‘You’re right, dammit. That’s precisely why I wanted you aboard, Snowy. Different ways of thinking, from a different biological perspective. A way to shed preconceptions we never knew we had. What is the point of the Long Earth if we can’t pool our minds?’ She studied the beagle. ‘I do hope you’re forming a more constructive impression of us, crewman, than I hear your people have on your home world.’