Hirata had known of the Rat’s origin in that far northern island known for cold winters and the copious body hair of the natives. “Speaking of Hokkaido,” he said, “I’m looking for someone from there.” He wondered if Lady Wisteria’s lover was as hairy as the Rat, and shaved to blend with the Edo locals. “Have you come across any of your countrymen around town?”

Because the Rat collected news and had served as a reliable informant in the past, Hirata hoped for a lead on Wisteria’s lover, but the Rat shook his head.

“Haven’t seen or heard of any Hokkaido folk in these parts for years,” he said. “Far as I know, I’m the only one in Edo now.”

An idea occurred to Hirata, and though it seemed ludicrous, he had to ask: “Have you been seeing a courtesan named Wisteria?”

“Me? Why, no.” The Rat looked dumbfounded, then guffawed. “Oh, you’re joking. Even if I could afford Yoshiwara, those women would run screaming from me.”

Hirata experienced discouragement, because if the Rat knew nothing of Wisteria’s lover, then the man had kept himself well hidden. Or perhaps the pages he’d bought from Gorobei were a false clue, as Reiko had suggested. “Let me know anything you hear about a Hokkaido man, particularly one traveling with a woman,” Hirata said.

“Will do.” The Rat ambled away with his monkey.

Impatient for action, Hirata decided to press onward to Fukagawa and search the noodle shops where Lady Wisteria and her lover might have taken refuge. But first he would visit his family and test the chances of his marriage to Midori.

A horde of bureaucrats paraded in and out of Sano’s mansion, all with the intent of heaping suspicion on their enemies. They besieged Sano with unsubstantiated accusations until his mind whirled. By midmorning he couldn’t endure any more self-serving attempts to manipulate him. Finally, during a break between calls, Sano donned his outdoor clothes and swords, then left the house in search of the one person who could tell him which rumors were true or false.

The day was cold and bleak, the sky like raw, soiled cotton, the moist air gritty with soot. Below Edo Castle, the steel-gray river and canals carved a monotone cityscape. The hazy peaks of the hills outside town smudged the distance. Sano passed hurrying officials and patrolling troops as he ascended through the castle’s stone-walled passages. Everyone’s expression appeared as dismal as the weather. Sano walked faster, uneasy in the tension created by Lord Mitsuyoshi’s murder; he could almost smell the impending purge in the air. Entering the palace, he proceeded to a secluded area in which he’d first set foot a lifetime ago.

Here, hidden within a labyrinth of corridors, government offices, and reception rooms, lay the headquarters of the metsuke. The Tokugawa intelligence service occupied a room whose mean proportions belied its power. In compartments divided by paper-and-wood screens, men smoked tobacco pipes and studied maps hung on the walls; they conversed together or pored over papers at desks laden with scrolls, message containers, books, and writing implements. As Sano passed, heads turned toward him, and voices lowered.

Inside the last compartment knelt a samurai dressed in black. He looked up from reading a ledger and bowed to Sano. “Greetings, Sōsakan-sama.”

Sano returned the bow. "Greetings, Toda-san.”

Toda Ikkyu was a senior intelligence agent, and of such nondescript appearance that Sano might not recognize him if they met anywhere else. Neither short nor tall, fat nor thin, old nor young, Toda had weary eyes set in a face that no one would notice in a crowd. Sano had consulted Toda on past cases, and Toda had once described how he’d spied on an official suspected of treason. The official never recognized Toda, although they both worked in the palace and passed each other in the corridors daily. He went to his death on the execution ground without knowing who’d sent him there.

“Can you spare me a moment of your time?” Sano asked, imagining that he might someday find himself the unwitting prey of the metsuke agent.

“Certainly.” Toda motioned for Sano to sit near him. His languid voice and gesture belonged to a man who seldom roused from a natural state of ennui. “I suppose this visit concerns your investigation of Lord Mitsuyoshi’s murder?”

“Yes,” Sano said.

“And you’ve come to me because you’re deluged with rumors.”

Sano chuckled, because the extent of Toda’s knowledge never ceased to amaze him. Toda also chuckled.

“It never ceases to amaze me how far you’ve risen in the world since we first met,” Toda said.

They’d met during Sano’s first murder case, when Sano had discovered a plot against the shogun and had come to Edo Castle to report it to the metsuke.

“To go from renegade policeman on a personal crusade to Most Honorable Investigator for His Excellency is no small accomplishment,” Toda said. “That you’ve kept the post for four years is a miracle, considering all the troubles you’ve had.”

“Is it any more a miracle than that you’ve kept your post in spite of all your troubles?” Sano couldn’t resist saying.

Toda had disbelieved Sano’s story about the plot, and later, the shogun had punished the entire metsuke for failing to take the threat seriously. Agents had been demoted, banished, and executed, yet Toda had somehow survived. Sano suspected that Toda knew the secrets of many members of the bakufu’s upper echelon, and had blackmailed them into protecting him.

Now Toda smiled complacently. “We’ve both been fortunate,” he said.

“Good fortune is an impermanent condition,” Sano said, “but perhaps we can maintain ours by working together.”

Toda’s expression didn’t change, but Sano felt the man’s resistance to the hint that he’d better grant the favor Sano was about to ask. Metsuke agents had a habit of hoarding facts. They liked to know things that others didn’t, they jealously guarded their unique power, and they wanted sole credit for keeping Japan under the bakufu’s control. But sometimes their habit backfired on them.

After the Black Lotus crisis, a disturbing fact had come to light: The metsuke possessed years of records that described the sect’s illegal practices, yet had not only failed to prevent the sect from gaining an immense, dangerous following but had withheld their records from the Minister of Temples and Shrines, who’d tried to thwart the Black Lotus and asked the metsuke’s help. Further investigation revealed sect members within the ranks of the metsuke. Toda had survived the purge that ensued, but even he wasn’t invincible. The murder of Lord Mitsuyoshi was such a politically sensitive issue that for Toda to refuse to cooperate with Sano’s investigation equaled suicide.

“What can I do for you?” Toda said with weary capitulation.

“Let’s start with Treasury Minister Nitta,” Sano said.

The agent looked around the office, then rose and said, “Let’s go elsewhere, shall we?”

Soon they were walking along the Edo Castle racetrack. In summer, this was the scene of samurai riding horses at a furious pace, while palace officials cheered. But now the track was a bare strip of earth, the benches vacant; only a faint smell of manure lingered. An empty meadow, surrounded by pine trees and stone walls, isolated Sano and Toda.

“Is it true that Nitta embezzles from the treasury?” Sano said.

Toda looked as though he’d guessed what Sano would say, but frowned, nonetheless perturbed. “Where did you hear that?”

“Nitta seems to have mentioned it to Lady Wisteria, who told another client,” Sano said.

“Well, he’s the subject of a highly confidential investigation,” Toda said. “I’m surprised that Nitta would incriminate himself, but men are sometimes careless about what they tell courtesans.”