There was nothing one could see to give cause for this.  A flock of curlew were passing, wailing one to the other, across the sunset; a string of late gulls trailed athwart the sky; and a wedge of those beautiful little wild-duck known as wigeon was letting itself down to the shores of the inlet.  Far out to sea a black line, which might have been a sea-serpent if it hadn’t been scoter ducks, trailed undulating over the waves, and a single great white gannet plunged from aloft into the deep at intervals with a report like a sunset gun.  But they were all innocent, except in the opinion of the fish and shell-fish, and no manner of folk to trouble the pirate skua.  Set a thief to catch a thief, however.  And, besides, there was blood on the bird and around him, or the taint of it, and blood is the devil and all in the wild.  There was nothing to be seen.  No.  That was the worst part of it.  It was what was unseen that the skua was thinking about.

Wherefore, then, our friend of the pirate rig rose and walked stiffly to the summit of one of the bowlder-rocks right at the water’s edge.  He was by no means recovered yet, or in any condition for a fight in that desolate scene, and had to select the most strategic position he could crawl to.  He did, and awaited Fate’s reply.

The day died, and the moon came out to wink and dodge and play a foolish game of hide-and-seek in and out among the clouds.  She showed the skua, a black knob atop of the black blob of his bowlder, apparently fast asleep, invisible if we did not know he was there.  She showed black dots bobbing upon silver lanes, which were sea-duck of various kinds—­scaup, long tail, scoter, and the rest.  She showed a line of old, rotten posts, broken off short by the waves, along a sand-ridge, which were wild-geese; and she showed three big, white swans—­wild-swans, wilder even than the geese—­floating like ghosts in the enchanted light.

But she also showed other things, indistinctly, ’tis true; but enough—­quite enough.  She revealed for an instant, as she shone on the spot on the sand where the skua had sat, the fact that the sand seemed to be alive, horribly alive, as if the pebbles had taken legs and ran about.  It was a sudden, ghastly flashlight, hidden as soon as seen, and it gave one the shudders.  Those pebbles were crabs mad with hunger, as crabs always seem to he.

They had arrived there as if by magic—­been creeping in ever since dusk, probably (one of the things that were unseen); but whether blood, or feathers, or taint of blood, or what horrible, ghoulish system of espionage drew them, is not for me to say.  They were there, anyway, and—­and—­well, and then they were not there.  The next flashlight of the moon showed that some others had taken their place.  This was ghastly, for the others were bigger than any shore crabs, and they hopped, and they sat up hunched, like hobgoblins, and—­they scratched!  This last identified them, for the