Prime Minister Su gazed at his wife's handwriting on the letter and suddenly let out a trapped animal's wail. He slumped down among the files on the floor and grabbed his wife's dressing box from the desk. Inside lay a half-used bottle of black ink—he had bought it from a Persian merchant. His wife always jokingly said, "The black ink is as beautiful as distant mountains, but it's not even a fraction as beautiful as your eyes and eyebrows." Now the color remains, but the woman has turned to dust, her death buried for over a decade.

"It's me... I've failed you..." He huddled on the ground, clutching his dressing box. His silver beard brushed against the cold mirror, revealing a tearful face. The rainstorm reached its peak, bathing the eaves and ridges of the prime minister's residence in inky black. Only the flickering firelight in the study illuminated the messy truth and belated regret.

Su Jinli gazed at her father's hunched back, and suddenly felt the grievances of past and present lives flood back like a tide. She remembered Liu's feigned tears as she pushed her into the bridal sedan, the drunken slap from the Wang family's son, and the desolate death of herself, left without even a bowl of hot soup. And the source of all this, surprisingly, was her father's neglect and trust.

"Dad..." She crouched down, wanting to offer comfort but unsure where to begin. Young Marquis Su suddenly slammed his gilded axe to the ground with a dull thud. "It's all my fault! If I'd grown up sooner, I'd have chopped off those bastards' heads!" The young man's voice was tinged with tears, but when he met his sister's gaze, he forced the tears back.

Jiang Yan silently picked up the hangover soup from the floor and wiped the blood off the edge of the bowl with a handkerchief. "Father-in-law, the most urgent task is to find evidence of Doctor Zhou's guilt." He pushed his glasses up, his gaze sharp as a knife. "Old Lady Wang confessed that there was an account book that recorded the source of the poison."

Prime Minister Su suddenly looked up, a glimmer of clarity in his eyes. "Account books... When Imperial Physician Zhou retired, he gave me a copy of Thousand Golden Prescriptions..." He struggled to point to the top shelf, but his drunkenness caused him to stumble again. Su Jinli and Jiang Yan exchanged a glance. The latter had already leaped onto the bookshelf, his fingertips darting across the spines of the books, finally resting on an ancient tome bound in a blue cloth cover.

"Found it!" Jiang Yan flipped open the book, and the parchment ledger rustled inside. The moment Su Jinli took the ledger, she heard her father's chuckle behind her. Turning back, she saw him holding his wife's dressing box, his face buried in it, like a lost child.

The rainstorm gradually subsided, and the sky in the east began to turn pale. Su Jinli looked at the imperial physician's seal on the account book last week, then at her father, who lay curled up on the ground. Suddenly, she felt that this half-life of regret was like the rain outside the window: it would eventually subside, but it had left an indelible mark on everyone's heart. And this pursuit of the truth had only just begun its most daunting prelude.