He pulled out a drawer. Throwing the papers inside carelessly on the floor, he searched with feverish haste for the traced copy of the inscription that Willow Down had given to him.

He found it rolled up in the back of the drawer. He quickly unrolled it on his desk and placed a paperweight on either end. Then he took the printed sheet with the chess problem and laid it next to the text. He carefully compared the two.

The Buddhist text consisted of exactly sixty-four words, arranged in eight columns of eight words each. It was indeed a perfect square. Judge Dee knitted his bushy eyebrows. The chess problem also was a square, but here the surface was divided into eighteen columns of eighteen squares each. And even if the similarity in design had a special meaning, what could be the connection between a Buddhist text and a chess problem?

The judge forced himself to think calmly. The text was taken verbatim from a famous old Buddhist book. It could hardly be used for concealing a hidden meaning without substantial alterations in the wording. Therefore the clue to die relation of the two, if any, was evidently contained in the chess problem.

He slowly tugged at his whiskers. It had been established without doubt that the chess problem was in reality no problem at all. Chiao Tai had observed that the white and black men seemed to be distributed over the board at random; especially, black's position didn't make any sense at all. Judge Dee's eyes narrowed. What if the clue were contained in the black position, the white men being added afterward, merely as camouflage?

He quickly counted the points occupied by the black men. They were spread over an area eight by eight square. The sixty-four words of the Buddhist text were arranged in exactly the same way!

The judge grabbed his writing brush. Consulting the chess problem, he drew circles round seventeen words in the Buddhist text, occurring on the places indicated by the black men. He heaved a deep sigh. The seventeen words read together made a sentence that could have but one meaning. The riddle was solved!

He threw the brush down and wiped the perspiration from his forehead. Now he knew where the headquarters of the White Lotus sect were located.

He rose and walked briskly to the door. His four assistants were standing huddled together in a corner of the corridor outside, unhappily discussing in whispers the possible causes for Judge Dee's despair. He motioned them to come inside.

When they entered his office they immediately saw that the crisis had been tided over. Judge Dee was standing very straight in front of the desk, his arms folded in his wide sleeves. Fixing them with burning eyes, he spoke.

"Tonight I shall clear up the case of the strangled courtesan. I have now finally understood her last message!"

Gathering his four assistants round him, Judge Dee unfolded his plan in a hurried whisper. "Be very careful!" he concluded. "There's treason here in this tribunal; the walls have ears!"

When Ma Joong and Chiao Tai had rushed outside, the judge said to Sergeant Hoong:

"Go to the guardhouse, Hoong, and keep an eye on the guards and constables there. As soon as you see that one of them is approached by someone from outside, you have both of them arrested at once!"

Then the judge left his office, and ascended together with Tao Gan the staircase to the second floor of the tribunal. They went out on the marble terrace.

Judge Dee anxiously looked up at the sky. There was a brilliant moon and the air was hot and still. He held up his hand. There was not the slightest breeze. With a sigh of relief he sat down near the balustrade.

Resting his chin in his cupped hands, the judge looked out over the dark city. It was past the first night watch; people were putting out the lights. Tao Gan remained standing behind Judge Dee's chair. Fingering the long hairs that sprouted from his cheek, he stared into the distance.

They remained there in silence for a long time. From the street below came the sound of a clapper. The night watch was making his rounds.

Judge Dee rose abruptly.

"It's getting late!" he remarked.

"It's not an easy job, Your Honor!" Tao Gan said reassuringly.

"It may take more time than we thought!"

Suddenly the judge clutched Tao Gan's sleeve.

"Look!" he exclaimed. "It's starting!"

In eastern direction a column of gray smoke was rising above the rooftops. A thin flame shot up.

"Come along!" Judge Dee called out. He ran down the stairs.

As they arrived in the courtyard below the large gong at the gate of the tribunal raised its bronze voice. Two stalwart guards were beating it with heavy wooden clubs. The fire had been spotted.

Constables and guards came running out of their quarters fastening the straps of their helmets.

"All of you go to the fire!" Judge Dee commanded. "Two guards stay behind here at the gate!"

Then he ran out into the street, followed by Tao Gan.

They found the large gate of the Han mansion wide open. The last servants came running out carrying their belongings in hastily made bundles. The flames were licking at the roof of the storeroom at the back of the house. A crowd of citizens had assembled in the street outside. Under the direction of the warden of that quarter they were forming a chain, handing on buckets of water to the constables standing on the garden wall.

Judge Dee stood himself in front of the gate. He called out in a stentorious voice:

"Two constables will stand guard here! Let no thieves or marauders slip inside! I'll go and see whether anyone is left behind!"

He rushed with Tao Gan into the deserted compound. They went straight to the Buddhist Chapel.

Standing in front of the altar, Judge Dee took the traced copy of tie Buddhist text from his sleeve and quickly pointed at the seventeen words he had marked with his brush.

"Look!" he said, "this sentence is the key to the letter lock of the jade panel: 'If ye understand My Message and depress these words ye shall enter this Gate and find peace.' That can only mean that the jade panel is a door that gives access to a secret room. You hold the paper!"

The judge pressed his index on the jade square with the word "if" in the first line. The square receded a little. He pressed harder, using both thumbs. The square receded half an inch; then it would go no farther. The judge went on to the word "ye" in the next line. That square also could be pressed down. When he had pressed the word "peace" in the last line, he suddenly heard a faint click. He pushed the panel and it slowly swung inward, revealing a dark opening of four feet square.

Judge Dee took over the lantern from Tao Gan and crept inside.

When Tao Gan had followed his example, he noticed that the door slowly closed again. He quickly grabbed the knob on its inside and turned it round. He found to his relief that thus he could pull the door open again.

The judge had gone ahead through the low tunnel. After about ten steps it became higher and he could stand upright. The light of the lantern revealed a flight of steep steps leading down into the darkness below. The judge descended, counting twenty steps. He stood in a crypt of about fifteen feet square, hewn from the solid rock. Along the wall on his right stood a dozen large earthenware jars, their mouths sealed with thick parchment. One of the covers was torn. Judge Dee put his hand inside and brought out a handful of dried rice. On the left they saw an iron door; ahead there was a dark archway, giving access to another tunnel. Judge Dee turned the knob of the door. It swung inside noiselessly on well-oiled hinges. He stood stock-still.