“Are those his only observations?” Sano asked, concerned not just because they were so limited.

When Fukida nodded, Marume said, “What else do we need to know?”

“Where Lord Mori got them would be helpful.” Sano wondered why Hirata had left an important task to his subordinate, apparently without checking the results.

“That might tell us who was conspiring with him to overthrow Lord Matsudaira,” Marume agreed. “But didn’t Hirata-ran say he searched the crates for documents to show where the guns came from and didn’t find any?”

“Yes. But documents aren’t the only means of tracing guns.” Sano thought Hirata should have been aware of this fact, should have taken it into account. “Help me inspect these for gunmaker’s marks.”

Looking over each gun, they found characters and crests, etched into the barrels or branded on the wooden stocks, that identified the craftsmen who’d made them. “Four different gunmakers so far,” Marume said after they’d gone through twenty crates. “Two of them have big workshops in Edo. They supply guns to the Tokugawa army.”

“Maybe someone in the army is in on the conspiracy,” Fukida said.

“They also make guns for the daimyo,” said Marume. “Don’t count them out.”

These possibilities heartened Sano. The army and the daimyo class could offer plenty of treason suspects besides himself-but he shouldn’t jump to conclusions. “There have been thefts from the arsenal during the three years since the war,” Sano pointed out. “These guns could have gotten into Lord Mori’s warehouse via the black market.”

“I don’t recognize the other two marks,” Fukida said.

Nor did Sano. “They must belong to craftsmen in the provinces.”

He and his men were down to the last three crates. As soon as Sano lifted out a gun he saw on its stock a circular crest with a chevron inside. He felt a mixture of triumph and dismay.

“Is something wrong?” Fukida asked.

“That’s a new mark,” Marume said, peering at the gun. “I don’t recognize it.”

“Neither do I,” said Fukida.

“I do,” Sano said. He had good reason to, whereas his men didn’t and neither did Detective Arai, who’d done the inventory and overlooked the marks. “It belongs to a workshop in the Hatchobori district. They make guns for the Edo police force.”

“I didn’t know the police had guns,” Marume said. “They don’t carry them.”

“Many of the commanders have them for target practice. That’s their hobby.” A former police commander himself, Sano knew this. “They’ve built up quite a collection.”

“This is just what we’ve been looking for.” Excitement animated Fukida’s serious features. “A clue that points to Police Commissioner Hoshina.”

“He could have been putting together a gang to overthrow Lord Matsudaira’s regime and do away with you at the same time,” Marume said to Sano.

“Maybe he recruited Lord Mori and put him in charge of collecting guns for another war,” Fukida said.

“Maybe Lord Mori had second thoughts,” Marume said, “and Hoshina was afraid he would report the conspiracy. That would explain why he’d have wanted Lord Mori dead.”

“What if he went to the Mori estate and happened to see Lady Reiko there?” Fukida speculated.

Marume pantomimed shooting a bow and arrow. “Two birds at once. Down goes Chamberlain Sano as well as Lord Mori.”

The detectives had followed Sano’s line of thought to a conclusion that obviously delighted them. Sano was gladdened, too, that the guns had implicated Hoshina in murder and treason, but less happy about how and when this clue had come to light.

Fukida handled a gun, frowning at the telltale mark. “I wonder why Sosakan Hirata didn’t notice this. He used to be a police officer.”

“It seems as if he’d have recognized-” Marume interrupted himself. He and Fukida glanced at Sano, then away.

An uncomfortable silence fell.

Sano knew they were thinking the same thing he was: Hirata didn’t even look for the marks. He missed an important clue.

“No harm done,” Marume said, too loudly.

“We have the evidence against Hoshina now,” Fukida said.

Sano sensed their desire to protect Hirata, their friend and former comrade. He tried not to calculate what Hirata’s mistake might have cost him, although he couldn’t help wondering, What if I’d had this information about the guns yesterday?

He said, “Do you think we have time for a ride to the police district before the rain starts again?”

Marume and Fukida grinned, happy at the prospect of gathering more timber for Hoshina’s funeral pyre. “We have time, rain or not,” Marume said.

Quays and warehouses abounded in Hatchobori, the district where the police commanders known as joriki lived in estates grouped together like an island amid the townspeople’s dwellings. They were famous for the airs they put on and the bribes they took. As Sano rode along a quay with his entourage, they passed a joriki riding with his attendants. Sano recognized him as Hayashi, a former colleague. He wore expensive chain mail, probably his latest gift from a lord whose retainers had gotten in a brawl and who’d paid him to hush up the affair. He bowed coldly to Sano: He still resented the fact that Sano had been promoted over him, especially because Sano had been a misfit in the exclusive police brotherhood.

The shooting range was a favorite haunt of the joriki. It was surrounded by wharves for firewood and bamboo poles, invisible behind a wall topped with sharp iron spikes. Lanterns hung over the gate flamed and smoked in the damp evening air. Two samurai youths lolled inside a guard booth. When Sano’s party stopped before them, they rose and bowed.

“Chamberlain Sano wants to go inside,” Detective Marume said.

The guards exchanged fearful glances that seemed an odd response to such a simple request. They had similar square jaws and chunky physiques; they looked like brothers. One said, “I’m sorry, but we’re closed today.”

“The field is flooded,” the other hastened to explain.

“That’s no problem,” said Marume. “Chamberlain Sano isn’t here to shoot. He only needs to see the guns.”

The guards spoke in rapid, panicky succession: “Nobody except the police commanders is allowed in the arsenal.” “Police Commissioner Hoshina’s orders.”

“The honorable chamberlain outranks your boss,” Marume said. “Open up.”

The guards reluctantly obeyed. Riding in, Sano asked them, “Who’s the caretaker of the arsenal these days?”

“Me,” mumbled the younger man.

“Come with us.”

Inside was a long patch of muddy ground, weed-covered in some places, under water in low spots. At one end stood flat, wooden, man-shaped figures riddled with bullet holes and a suit of armor mounted on a wicker horse. Opposite was the arsenal, a shed with stone walls, an iron-shingled roof, and an iron door and shutters. A similar, smaller building held ammunition and gunpowder. As Sano and his men rode toward the arsenal, he heard his name shouted. He turned and saw Captain Torai, chief retainer to Police Commissioner Hoshina, riding after them so hard that his horse’s hooves splashed up fountains of water.

“What a surprise to see you here,” Torai said as he caught up with Sano. “I didn’t know you were interested in shooting.”

“Only when I see someone I’d like to shoot,” Sano said.

Torai’s grin gave his face a wolfish cast. “May I be of assistance?” he said, obviously eager to find out what Sano was up to.

“No, thank you.” Sano kept riding.

“He wants to see the guns,” blurted the caretaker, who hurried alongside him on foot.

“Oh?” Torai sped up his horse, placing himself between the arsenal and Sano. “Why?”

“Just testing a theory,” Sano said.

Torai blocked the door to the arsenal. “What theory?”