Then an intriguing alternative occurred to Sano. The killer, whoever he was, would want his ancestor’s precious, incriminating sword back-Chūgo or Matsui to avoid punishment, Yanagisawa to avoid scandal and bother. The killer seemed to know it was Madam Shimizu who had seen him, and to fear she would report him. Sano saw a way to use this knowledge, and the circumstances at hand.

“I need a favor from you,” he said to Madam Shimizu as he rewrapped the sword.

Her plump chin trembled, and she looked at him fearfully. “Haven’t I given you enough already? Why must I do you a favor?”

“Because if you don’t, I won’t keep silent about your trip to the temple and what you saw there. I’ll make you testify at the killer’s trial, and everyone-including your husband-will know what you did.”

Even as he pressured Madam Shimizu, Sano hated his treatment of this miserable, helpless woman. With sudden frightening insight, he realized that this was how one rose within the bakufu. You used your knowledge and position to bend others to your will, to achieve your purposes. Until one day you ended up like Chamberlain Yanagisawa… Sano’s quest had brought him this understanding of his enemy, and of how much similarity existed between them. Now he swallowed his self-disgust, telling himself that his goal justified the means-as Yanagisawa probably did while he dominated the shogun, ruined lives, and squandered treasury funds.

“I see I have no choice but to honor your wishes,” Madam Shimizu was saying.

Then, to Sano’s surprise, she lifted her chin and smiled. She laid a hand on his arm, gazing coquettishly up at him. A strange mixture of fear and gratitude filled her eyes. Sano saw with pity that she thought he wanted her to service him sexually. Furthermore, she welcomed his request as proof of her desirability, and to assuage the pain of her husband’s rejection.

“I’m sorry, Madam Shimizu, but I couldn’t force myself on you,” he said gently, putting her hand away from him in feigned regret.

And, while her expression changed from disappointment to surprised alarm, he told her how she could help him deliver the Bundori Killer to justice.

When he got back to town, Sano found Hirata riding back and forth along the promenade outside the castle gate.

“Sumimasen-I’m sorry to report that I couldn’t follow Chamberlain Yanagisawa because he hasn’t come out,” Hirata said gloomily.

“Never mind. Let’s go.” Sano slapped his horse’s reins.

Hirata hurried to catch up. “Where? Why?”

“We’re going to set a trap for the Bundori Killer.”

They rode through the daimyo district, into Nihonbashi. Sano told Hirata what he’d learned from Madam Shimizu, and about the sword now hidden in his saddlebag. But he couldn’t specify the details of his plan until they’d scouted the location.

Once across the Nihonbashi Bridge, Sano led the way east, then north up the wide firebreak along the Sumida River, past warehouses and through the crowds around the teahouses, food stalls, and entertainment halls at the foot of the Ryōgoku Bridge, to the Kanda River-an aqueduct that emptied into the Sumida.

“Here,” Sano said, turning left onto the path bordering the Kanda. Hirata, looking puzzled, followed.

The path sloped upward to run along the top of the river’s vertical, stone-faced bank. On Sano’s left rose affluent merchants’ houses with balconies overlooking the river. To the right, a wooden rail shielded the drop to the water. Docks jutted out from the path. At the end of these floated pleasure boats, all of which faced east toward the Sumida, with sloping gangplanks lowered from their decks. A wooden bridge gave access to the Kanda’s opposite side, which offered a similar scene.

“I don’t understand,” Hirata said.

By the fourth dock, Sano dismounted and tied the reins to the rail. “This is Madam Shimizu’s boat,” he explained. “We’ll set the trap here.”

At the villa, Madam Shimizu’s mention of the romantic boat trips she’d once enjoyed with her husband had inspired Sano. The boat’s location was near the city center, convenient to all three suspects, and yet relatively isolated, preventing interference from passersby. The layout, with its enclosed cabin and limited means of access and escape, would allow him to capture Chūgo or Matsui-or kill Yanagisawa and himself. He’d persuaded Madam Shimizu to let him set his trap on the boat, because if the Bundori Killer was indeed looking for her, then he would come here willingly to find her. Now Sano saw how well he’d chosen.

Made of cedarwood, the boat was perhaps fifty paces long. Both ends swooped gracefully up out of the water. At the stern, the deck tapered to a high viewing platform. The bow bore the boat’s figurehead-a likeness of a younger, lovely Madam Shimizu, lips smiling, long hair rippling. The cabin had a red shingled roof with upturned eaves. A single sail, furled around its tall mast, rose from the foredeck. Along the railed gunwales stood poles for hanging lanterns or banners. With its shallow draft, single pair of oars, and open rudder chamber, the boat was not a seaworthy vessel-the bakufu, to keep citizens from leaving the country, forbade the building of private craft equipped for rough waters. But the boat would suit Sano’s purpose admirably.

Sano turned his attention to the surroundings. Like Madam Shimizu’s, most of the other vessels were deserted; the boating season wouldn’t begin for another month or so. Sano squinted up at the sky, where the strengthening wind had blown more clouds in from the sea to the east.

“Not much chance of anyone setting sail tomorrow if this keeps up,” Sano remarked with satisfaction.

He was equally glad to see only a few people about: a maid hanging laundry on a balcony; a street vendor carrying a load of baskets across the bridge, where an old man stood fishing. The Shimizu boat was far enough from the Sumida’s heavy water traffic and the crowded firebreak so that any activity here would go unobserved.

“We’ll come early tomorrow and clear the area,” Sano told Hirata. “Your assistants can keep everyone away while we wait for the killer.”

Hirata’s face brightened with comprehension. “Aboard the boat.”

“Right.” Sano crossed the dock and ascended the creaking gangplank onto the boat, circling the deck. Not being a sailor, he made only a cursory inspection of the bow, where he found the anchor-a large, multipronged iron hook lying atop a heap of straw cable-near the sail. Then he more thoroughly examined the features of the boat that most concerned him. Beneath the hatch on the aft deck, in front of the tiller, he found coiled ropes, folded sails, a toolbox, lanterns, lamps, candles, water-tight metal containers of matches, and ceramic jars of water, oil, and sake. He opened the cabin door and entered a spacious, low-ceilinged compartment lined with silk-cushioned benches. Windows, equipped with slatted shutters that could be adjusted to let in light and air, overlooked the port and starboard decks. Sano’s search of the cupboards turned up folded bedding and clothes. Drawers under the benches held dishware, napkins, chopsticks, chamberpots, soap, toiletries, and bundles of dried fish, seaweed, and fruits. Madam Shimizu, hoping in vain for her husband’s love to return, had kept the boat provisioned for a trip they would probably never take.

Behind Sano, Hirata spoke. “What do we do if-when-the killer comes?”

Sano stalled by going to the window and opening the shutters.

He hated to involve Hirata in his dangerous quest for justice and honor, but he needed the doshin’s help.

“If the killer is Matsui or Chūgo, you and your assistants will help me capture him-alive so he can be tried and punished for his crimes,” he said, pretending an interest in the view. “We’ll tie him with ropes from the hold and take him to Edo Jail.”