The drill code of the crab-guards has a first article of exactly two words: No retreat.
The second article explains the first: a crab has no neck and cannot look back. A creature born unable to look back belongs, by nature, in the last rank — wherever there is no ground left to give, that ground is ours.
So wherever the Water Court's defenses meet a place of last resort, you will find a crab-guard standing on it.
My place of last resort — believe it or not — is a door.
Nineteen li out from the palace, on the old reef-table, coral has wrapped the rock for ten thousand years into a small mountain. Set into its belly is a door: two men high, bronze-dark, no keyhole, no ring, its seam too fine for the thinnest blade. My family has stood before this door for eleven generations. At the handing-over, my father passed me the halberd with a single instruction: Stand. Don't ask.
I asked anyway: what's inside?
He said: eleven generations now. Nobody knows.
Laughable, you may think. A soldier spending his whole life guarding a door that leads nobody-knows-where. The young shrimps passing on patrol laugh too: brother crab, are you sure that's not just a wall? I take no offense. Article one says no retreat. No article says pay attention to those who laugh.
Besides — this door is no wall.
Walls don't knock.
Once a year, on the night of the lunar eclipse only, at the moment the moon goes blackest, a knocking comes from the other side — tok. Tok. Tok. Three. No more, no fewer. Not loud. Like knuckles rapping politely through something very thick.
Eleven generations have heard it. My father heard it forty times. As of this year, I have heard it fifty-three.
In my early years I took it for a cry for help, and beat the door with my halberd, shouting. No answer. The knocking never hurried by a beat, never slowed by one; the next eclipse, three knocks again, the same. Slowly I came to taste what it really was. A cry for help is ragged, urgent. These three strokes are steady — steady like the keeping of an appointment.
Like a question: are you still there?
So the thirtieth time I heard it, I did something. When the three strokes settled, I raised my halberd's shaft and knocked three times in reply.
Beyond the door: silence, long, long silence.
Then — softly — one knock back. Just one.
Since that year, this has been the custom between me and the far side. It knocks three; I answer three; it closes with one; and the year is complete. I do not know what it is. It does not know what I am. Yet for the first time in eleven generations, this door has gone from being a posting to being an acquaintance.
This year's eclipse is almost here. But this year is unlike the others — the tides have lost their order, the Sea-Calming Treasure is missing, and the gate-foot booms through the days. The children from the shore crossed my reef-table saying they mean to trace all of it to the root.
I told them about my door. And when I finished, the boy with the medicine basket asked the one question I have not dared ask in fifty-three years:
"Old brother — every year it knocks three times to ask if you're still there. What if, some year… it doesn't knock?"
I gripped my halberd and could not speak for a long time.
No retreat — that, I can do. But for the first time I understand there is something colder than the door opening —
and that is the day the far side goes silent.