I shall now proceed once more to your late father's library. You need not bother to accompany us."

They found two constables on guard in the dark corridor that led to the library. They reported that no one had even approached that place.

Judge Dee broke the seal and opened the door.

He hastily stepped backward covering his face with his long sleeve.

A nauseating smell assailed their nostrils.

"There is something dead in there", the judge said. "Go to the main hall, Tao Gan, and ask those priests for a few sticks of Indian incense!"

Tao Gan hurried away.

He came back with three lighted incense sticks in each hand. They made a dense smoke with a penetrating smell.

The judge took them and once more entered the library waving the sticks so that he was enveloped in a cloud of blue smoke.

The sergeant and Tao Gan waited outside.

After a while Judge Dee emerged. He was carrying a thin forked stick that is used for suspending scroll pictures on the wall. On its end rested the half decayed body of a mouse.

He handed the stick to Tao Gan and ordered: "Have the constables put this dead animal in a sealed box!"

Judge Dee remained standing in front of the open door. He had placed the sticks of incense in the brush holder on the desk inside. Clouds of smoke wafted out of the door.

As they were waiting for the stench to disappear Sergeant Hoong remarked with a smile:

"That little animal gave me quite a fright, Your Honour!"

Judge Dee's face was impassive.

"You will not laugh, Sergeant, after you have entered that room. It is full of the spirit of violent death!"

When Tao Gan had come back all three of them entered the library.

Judge Dee pointed to a small cardboard box that was lying on the floor.

"The other day", he said, "I left that box on the desk, next to the ink slab. It is the box with the sweet plums that we found in the General's sleeve. A mouse smelled them. See, its little feet are clearly visible in the dust that gathered on the desk."

The judge stooped and picked up the box carefully with two fingers. He laid it on the desk.

They saw that a corner of the cover had been gnawed away.

The judge opened the box. One plum of the nine was missing.

"This was the murderer's second weapon", Judge Dee said gravely. "These plums are poisoned!"

He ordered Tao Gan:

"Search the floor for that plum. Don't touch it!"

Tao Gan went down on his knees. He found the plum, half eaten, under one of the bookshelves.

Judge Dee took a toothpick from the seam of his robe and stuck it in the plum. He put it back in the box and replaced the cover.

"Wrap this box up in a sheet of oilpaper", he said to Sergeant Hoong. "We shall take it to the tribunal for further investigation."

The judge looked around. Then he shook his head.

"Let us return to the tribunal", he said. "Tao Gan will seal this door again, and the two constables shall remain on guard outside."

They walked back in silence.

As he entered his private office the judge called out to the clerks to bring a pot of hot tea.

He sat down behind his desk. Tao Gan and the sergeant sat down on their customary footstools.

Silently they drank a cup of tea.

Then Judge Dee spoke:

"Sergeant, let one of the runners go out and call that old coroner here!"

When the sergeant had gone the judge said to Tao Gan:

"This murder becomes more and more complicated. Before we have even determined how the murderer struck we find that he kept a second weapon in reserve. As soon as we find out that the accused Woo has a mysterious girl friend, we learn that also the complainant Ding has a secret lover!"

"Could not it be, Your Honour", Tao Gan said slyly, "that it is one and the same girl? If Woo and Ding are rivals in love, that would throw an entirely new light on the latter's accusation!"

Judge Dee looked pleased.

"That", he said, "is a very interesting suggestion!"

After a pause Tao Gan resumed:

"I still can't understand how the murderer succeeded in making General Ding accept that box with poisoned plums! The murderer must have handed it to him personally. We saw the pile of anniversary gifts on the table in the corridor. He would not have put it there, for how could he be sure that the General would pick up that particular box? It might have as well been taken by Candidate Ding or another member of the household."

"And then", the sergeant remarked, "we have also this problem: why did the murderer not remove this box from the General's sleeve after he had killed him? Why leave this piece of evidence on the scene of the crime?"

Tao Gan shook his head perplexedly. After a while he said:

"Seldom have we been confronted with so many difficult problems at the same time. Apart from this murder we have the hidden message in that landscape painting there on the wall, and all the while Chien Mow's mysterious visitor is still roaming about freely and planning Heaven knows what new mischief. Is there no clue to his identity at all?"

Judge Dee smiled bleakly.

"Nothing at all", he replied. "Last night Chiao Tai told me that he had interrogated Chien's former guards and his counsellors. None of them could supply any information. The mysterious stranger always came late at night and his long cloak concealed his build. He never spoke a word. The ower (lower) part of his face was covered by his neckcloth, the upper lpart (part) concealed by the shadow of his hood. He even did not show his hands, he always kept them inside his sleeves!"

They drank another cup of tea.

Then a clerk announced that the coroner had arrived.

Judge Dee gave the old drug dealer a sharp look.

"The other day when you performed the autopsy on the General's body", he said to him, "you stated that most poisons used internally can be identified. Now I have here a box with sweet plums. A mouse ate one and died on the spot. You will examine these plums in my presence and try to determine what poison they contain. If necessary you can also examine the dead mouse."

Judge Dee handed the cardboard box to the coroner.

The old man opened the small bundle he had brought and took out a leather folder. It contained a set of thin knives with short blades and long handles. He selected one that had a fine, hair-sharp blade.

Then he took a square pad of white paper from his sleeve and put it on the corner of the desk. He picked up with a pair of pincers the plum the mouse had eaten from and laid it on the pad. With remarkable dexterity he cut from its flesh a slice as thin as the thinnest tissue paper.

The judge and his two lieutenants eagerly followed his every movement.

The coroner smoothed out the slice on the pad using the blade of the knife. He peered intently at it. Then he looked up and asked for a cup of boiled water, an unused writing brush, and a candle.

When a clerk had brought the required materials, the coroner moistened the brush and soaked the thin slice in water. Then he took a small square piece of very white, glazed paper, spread it out over the slice and pressed it with the palm of his hand.

The coroner lighted the candle. He took up the glazed paper and showed it to the judge; it bore the wet imprint of the slice. The coroner held it over the flame till it had dried.

He took the paper over to the window and scrutinized it for some time, softly running his forefinger over it. Tao Gan left his chair and looked over the coroner's shoulder.

The coroner turned round and handed the paper to the judge. He said:

"I beg to report that this plum contains a large dose of a poisonous dye called gamboge. It was introduced by means of a hollow needle."

Judge Dee slowly caressed his whiskers. After a glance at the paper he asked: "How do you prove that?"