The morning mist enveloped the remains of the dragon kiln. Su Chen stepped on the charred bricks and peered inside. Tang Ren waved the torch and suddenly stumbled - a half-burned and deformed iron kiln was stuck in the soil, with a piece of celadon still stuck to the head.

"This, this is Yue kiln secret color porcelain!" Qin Feng scraped off the kiln sweat on the porcelain piece, "Shushan kiln has always fired celadon." Su Chen took out the red clay fragment in his arms for comparison. Under the firelight, the two glaze colors gradually blended together, revealing a crescent-shaped dark pattern.

The kiln worker's grandson trembled and pointed to the west slope: "Over there... the old kiln hole collapsed the other day..." When he touched the hole in three steps, he saw 23 pottery figurines kneeling beside the kiln hole, each holding broken porcelain in their hands. Tang Ren picked up a pottery figurine and tried to smash it, but the figurine's belly suddenly cracked open, and a string of copper-green keys rolled out.

The moment the key was inserted into the iron lock of the ancient kiln, Qin Feng suddenly grabbed Su Chen: "Lock, the lock core smells of sulfur!" Tang Ren quickly took out the cool tea he brought with him, and green smoke rose from the lock hole, etching out a bloody Q.

The deep part of the kiln was filled with celadon boxes. When the seventh layer was pried open, the entire stack of boxes suddenly collapsed. Su Chen caught the falling teapot. The mysterious color of the teapot was flowing in the firelight, reflecting the remaining pages of "The Classic of Tea". Tang Ren licked the mouth of the teapot: "Pah! It smells like rust."

"It's Crane Top Red." Su Chen rubbed his fingertips across the glaze, "The glaze is mixed with arsenic." As he spoke, a stone tablet suddenly fell from the top of the kiln. The inscription on the tablet recorded the poisonous porcelain case during the Guangxu period - the kiln worker involved was Master Li's great-grandfather.

When he returned to the medicine shop, he turned to the "Arsenic" page in the Compendium of Materia Medica on the counter. The apprentice Abao trembled and took out the account book: "The red calcite we just bought the day before yesterday is less, two kilograms..." Qin Feng suddenly pointed at the medicine cabinet: "The third row of drawers!"

Tang Ren opened the "Crane Top Red" drawer, which was filled with cinnabar mixed with celadon powder. Su Chen dipped his pen in water and wrote on the cabinet, and the water marks revealed a new palm print - exactly the same as the blood print on the willow tree of Baodai Bridge.

The night watchman's clappers suddenly sounded urgently, and screams came from the end of the street. When everyone rushed over, the new owner of Yongchang Pawnshop was lying dead in the backyard, holding a pawn ticket that read: "In the 23rd year of the reign of Emperor Guangxu, a pair of celadon teapots were pawned."

The sound of a pipa floated from the night-moored lantern boat, and Su Chen stared at the pair of secret-colored porcelain pots on the bow in a trance. The zither girl's fingertips swept across the strings, and the high pitch suddenly broke. Tang Renzong jumped onto the deck and ripped open the secret compartment in the zither's belly - it was filled with bloody tea tickets.

"This, this is the ticket from the secret compartment of the tea boat!" Qin Feng compared the handwriting. Su Chen turned the porcelain pot, and the spout suddenly sprayed out poisonous mist. Qin Niang tore off the leather mask, and it turned out to be the daughter of the kiln worker who had been missing for a long time. She smiled sadly: "There were 23 kiln workers, how many are left today?"

The pleasure boat suddenly tilted, and twenty-three celadon jars floated down the river. Tang Ren picked up a jar, and the bottom of the jar was engraved with the word "Chen" - it was three quarters of an hour tomorrow!

The sun was blazing, Su Chen was squeezed in the crowd and stared at the executioner's ghost-head knife. The red silk wrapped around the handle suddenly broke, and the light spots reflected by the blade spelled out the Big Dipper on the city wall. Qin Feng suddenly stuttered and shouted: "The blade is poisoned!"

Tang Ren sneaks into the prison execution room disguised as a food deliveryman, and tests the poisoned wine with a silver needle in the secret compartment of the food box. When the prefect is shocked and clap his hands, a strange wind suddenly blows in the execution ground. Su Chen throws out a copper coin to knock away the ghost-head knife, and the blue bricks burst where the knife falls, revealing the hidden "Blood Writing of Kiln Workers".

"March 23, Bingshen year..." Su Chen read the last line of the blood writing, his face changed suddenly - it was the day of the tragic case thirty years ago!

The moonlight was pale, and Sanyue returned to the Dragon Kiln. Su Chen turned the cauldron according to the blood-written record, and suddenly the kiln eye spurted out green flames. Tang Ren dug up the ashes, and 23 urns were neatly stacked, with the names of the kiln workers who died unjustly at that time engraved on the urn.

"One urn is missing..." Qin Feng counted to the 22nd and suddenly stopped. Footsteps were heard from deep inside the kiln, and the old grandson appeared holding the last urn: "When my father personally gave his apprentice a urn to keep the kiln fire alive..."

Before he finished speaking, the top of the kiln suddenly collapsed. Su Chen rolled out of the kiln with the urn in his arms, and heard the last roar of the old man from behind: "The blood debt of Heaven can never be repaid!"

The morning bell of Hanshan Temple cleared the mist, and Su Chen placed his ashes beside the Maple Bridge. Tang Ren chewed a freshly-cooked crab meat basket and muttered, "Is the case closed?" Qin Feng suddenly pointed to the river surface - 23 celadon cups were floating down the river, with a brand new Q engraved on the bottom of the cups.

The storyteller at Songhe Tower slammed the wooden board again, this time telling a secret story from the previous dynasty: "As for the origin of the Gongchun teapot, it was originally learned by a little monk..." Su Chen's hand that was stroking the teacup suddenly stopped. Purple bamboo patterns were faintly visible under the glaze of the cup - the material of the teaspoon in the teahouse murder case.

When the copper bells on the eaves rang again, the smoke from cooking in Suzhou City was still rising. No one noticed that the newly moored ship had an unusually deep draft, and twenty-three celadon jars were neatly stacked on the bottom of the ship...