“I didn’t love her,” Sano protested. “There was nothing between us but sex.” He saw Reiko’s eyes narrow. “It was just a brief affair that had no future.”

“Then why did you free her?” Reiko retorted. "Or didn’t you?” she added in a querulous tone that bespoke her need to believe he hadn’t performed this act that signified deep commitment to a courtesan.

“I did,” Sano said, though aware that the admission made him look guiltier.

Reiko briefly closed her eyes.

“But it wasn’t because I wanted the affair to go on.” Regretting to hurt her more, Sano nonetheless realized that he must tell her the whole story, and hastened to explain: “I met Wisteria on a case I investigated while I was on the police force. She gave me information. We spent a night together.”

“During which she taught you the art of lovemaking?”

Hearing the pain behind Reiko’s sarcasm, Sano nodded reluctantly. “Certain people were displeased that Wisteria helped me. She was punished. Her suffering was my fault, and I had to compensate her.” He described the events that had made this possible. “But I didn’t go to Yoshiwara to take her away.” Leafing through the book, he said, “There was no departure ceremony, no trip together to her new home. The bakufu provided the money and handled everything. Wisteria wasn’t my mistress. I never intended her to be.”

“So you were never together again?” Eagerness underlay Reiko’s skeptical query.

Though he hated to disappoint his wife, Sano said, “We were, but only twice-before you and I met. Wisteria was unfriendly to me. I was busy working for the shogun, and I never bothered going back to Wisteria. There were no violent quarrels, no reunions, no perverted sex, no insults toward the shogun, and certainly no scheme to use Masahiro-chan for my own benefit.”

Sano flung down the book, incensed anew by its portrayal of him. He was relieved that his secret had come out, but upset that it had come out this way. Gazing upon Reiko’s rigid, unhappy face, he said, “I love you. I’ve always been faithful to you.” Sincerity and tenderness hushed his voice: “I swear it on my life.”

Reiko looked torn between wanting to believe and wanting not to be deceived. Then she turned away. Sano inwardly cursed the Black Lotus for her morbid distrust that extended to him and what she knew in her heart about him.

“You’re always telling me that a good detective bases judgment on evidence,” she said. “What evidence is there to prove you’re not an adulterer?” She swallowed hard, as if to forestall crying. “What evidence is there to prove you weren’t involved in Lord Mitsuyoshi’s death?”

She even suspected him of murdering Mitsuyoshi so that Masahiro could take his place as the shogun’s heir! Sano lifted his eyes to the ceiling as despair filled him. He had nothing to prove the pillow book was a fraud. The only person who could say for a fact that he’d never done the things described in the book was Lady Wisteria. Sano thought of the mutilated corpse and shook his head. Then his gaze lit on the book, which lay on the table where he’d thrown it. A phrase that hadn’t registered while he read now jarred his memory. He snatched up the book and whipped through pages until he found it.

“Reiko-san, look,” he said.

She didn’t move. Eagerly Sano read aloud: “ ‘It was in the year that the child was born, during the month of leaves, while Sano-san and I sat on the roof viewing the full moon.’ But I couldn’t have been with Wisteria on the night of the full moon in the seventh month after you gave birth to Masahiro-chan. I was with you. Don’t you remember?”

Now Reiko did remember. She also remembered the passage in the book that she’d overlooked because she’d been too upset to read objectively. A rush of confused emotions made her feel faint. Stunned, she turned to Sano.

“Yes,” she said, and heard breathless relief in her voice.

Her distrust and his confession had transformed her husband into a stranger capable of adultery and treason; but now Sano looked his familiar self. An encouraging smile dawned through the worry on his face.

“The shogun had given you a holiday that month,” she said. “You took Masahiro-chan and me on a religious pilgrimage.” The temple where they’d stayed was a three-day journey from Edo, their holiday had lasted ten days total, and therefore Sano could not have gone to Wisteria in Nihonbashi at any time near the full moon.

“After you put Masahiro-chan to bed, you and I watched the moon from the garden,” Sano said.

“And we made love there.” The tears Reiko had been holding back now spilled. She wept with gladness that one small, false detail had shown the pillow book to be an elaborate lie, and shame that she’d not immediately recognized it as such. “Will you forgive me for doubting you?”

“If you forgive me for keeping a secret I should have told you,” Sano said.

He looked so earnest and chagrined that Reiko’s lingering anger melted away. Unaware of whether she moved toward him, or he toward her, she found herself and Sano embracing. She felt her sobs resonate through him, and the wetness on her cheek that could have been her tears or his. Sano’s hands caressed her with a tenderness that she could tell Lady Wisteria had never known from him. Her body responded with a welling of desire. His breath quickened and his grasp on her tightened.

Lovemaking would have followed, but they moved apart because they had serious matters to discuss. Reiko heated a vessel of sake, and they knelt with the pillow book and the tray of cups before them.

“If Wisteria didn’t write the book, who did?” Reiko said, pouring the steaming liquor.

Sano’s expression turned grim as he accepted a cup. “I can think of one person who would like me implicated in the murder and branded a traitor.”

“Yoriki Hoshina?”

Sano nodded. “Hoshina knows about the pillow book, and what it looks like, because he heard Wisteria’s kamuro describe it to me. Maybe he forged his own version and had it delivered anonymously to Chamberlain Yanagisawa. After that, all he had to do was wait.”

“For the chamberlain to use the book against you?” Reiko warmed her hands on her cup of sake before she drank. “But what about your truce with him?”

“The truce wouldn’t protect me in this case,” Sano said. He drained his cupful and poured himself another. “No matter if Yanagisawa wants us to remain at peace, he couldn’t ignore evidence that I insulted and plotted against the shogun or had reason to kill Lord Mitsuyoshi. He would have to give the book to the shogun, whether he believes I’m guilty or not.”

Now Reiko understood. “For him to shield a possible traitor would make him a traitor as well.”

“He might hesitate to act if he were the only one who knew about the evidence,” Sano said, “but he’s not. The author of the book also knows. And the author knows that Yanagisawa received the book. While Yanagisawa and I are no longer at war, we’re not exactly friends. He would never conceal the book and endanger himself for my sake. And Hoshina knows how his lover thinks. He’s been looking for a way to attack me.” Sano eyed the pillow book. “That must be his doing.”

In spite of the strong reasons to believe Hoshina had written the book, a different possibility occurred to Reiko.

“If Hoshina isn’t the author… ” Her voice trailed off because the idea seemed at once plausible and outlandish.

“Do you have someone else in mind?” Sano said.

“I’m thinking of Lady Yanagisawa,” Reiko said.

Sano regarded her with surprise. “How could she have known Wisteria had written a pillow book, or that it was missing?”

“Maybe she overheard the chamberlain and Hoshina discussing the case.”

“Even if she did, how would she have known what to write?”