Philips chuckled. “It’s good to see that distinguished scholars can retain a healthy sense of humor.”

“I try, sir, I try,” Stone said with a slow bow.

After Philips had left them, Caleb and Stone headed into the vault.

“How did you find out about Jonathan’s scholarly work?” Caleb asked once they were alone.

“I asked Milton to dig around. He located it on the Internet and brought me a copy. I scanned it in case someone like Philips showed up, to prove my scholarly pedigree.” Caleb looked disgruntled. “What’s the matter?” Stone asked.

“Well, it’s a little deflating to one’s ego to see how easily a scholar can be impersonated.”

“I’m sure your validation of my pedigree made all the difference to your boss.”

Caleb brightened. “Well, I’m sure it contributed somewhat to the success,” he said modestly.

“All right, take me through your exact movements that day.”

Caleb did so, ending on the top floor. He pointed at a spot. “That’s where his body was.” Caleb shivered. “God, it really was terrible.”

Stone looked around and then stopped and pointed at something on the wall.

“What’s that?”

Caleb looked to where he was pointing. “Oh, that’s a nozzle for the fire suppressant system.”

“You use water in here with all these books?”

“Oh, no. It’s a halon 1301 system.”

“Halon 1301?” Stone asked.

“It’s a gas, although it’s really a liquid, but when it shoots out of the nozzle, it turns to gas. It smothers the fire without damaging the books.”

Stone looked excited. “Smothers! My God!” His friend looked at him curiously. “Caleb, don’t you see?”

What Stone was referring to suddenly dawned on Caleb. “Smothering? Oh, no, Oliver, no. It couldn’t have been the cause of Jonathan’s death.”

“Why not?”

“Because a person would have several minutes to escape the area before he’d start feeling the effects. That’s why they use halon in occupied places. And before the gas is discharged, a warning horn comes on. We’re changing systems actually but not because it’s dangerous.”

“Why, then?”

“Halon significantly depletes the ozone layer. In fact, while it can still be used in this country and recycled for new applications, the manufacture of halon 1301 is banned in the U.S. and has been since the mid–nineties. Although the federal government is still the biggest user of it.”

“You seem to know a lot about halon.”

“Well, all employees were given an in–depth review of the system when it was first installed. And I did some extra reading on the subject.”

“Why?”

He blurted out, “Because I come into this vault a lot, and I didn’t want to die a horrible death! You know I lack any shred of personal courage.”

Stone examined the nozzle. “Where’s the gas stored?”

“Somewhere in the basement level of the building, and the gas is piped up here.”

“You say it’s stored as liquid and then comes out as a gas?”

“Yes. The speed with which it’s blown out of the nozzle turns it into a gas.”

“It must be very cold.”

“If you’re standing in front of the nozzle, you could get frostbite, in fact.”

“Anything else?”

“Well, if you stay in the room long enough, I suppose you could be asphyxiated. The rough rule of thumb is if there’s not enough oxygen for a fire, there’s not enough oxygen to sustain life.”

“Could the gas cause a heart attack?”

“I don’t know. But it doesn’t matter. The system never came on. That horn can be heard throughout the building. The only way Jonathan wouldn’t have heard it is if he was already dead.”

“What if the horn was disconnected?”

“Who would have done that?” Caleb said skeptically.

“I don’t know.”

While he was talking, Stone was staring at a large register built onto one of the columns supporting a bookshelf. “Is that a vent for the HVAC system?” he asked. Caleb nodded. “Something must have fallen on it,” Stone said, pointing to where two of the vent grilles had been bent.

“It happens with people bringing book carts in and out.”

Stone said, “I’ll have Milton research the halon system and see if anything else turns up. And Reuben has some friends at D.C. Homicide and the FBI from his days in military intelligence. I’ve asked Reuben to call them to see if he can find out something about the investigation.”

“We have the meeting with Vincent Pearl tonight at Jonathan’s house. In light of these developments, don’t you think it best to call it off?”

Stone shook his head. “No. Those men can find us wherever we are, Caleb. If we’re in danger, I’d rather try to find out the truth for myself than sit back and wait for the blow to fall.”

As they were leaving the vault, Caleb muttered, “Why couldn’t I have just joined a nice, boring book club?”

Chapter 22

That evening they all rode to DeHaven’s house in Caleb’s Nova. In the meantime Milton had found out a lot about fire suppressant systems. He reported that “halon 1301 is odorless and colorless, and extinguishes fires by tweaking the combustion process, which includes the depletion of oxygen levels. It evaporates quickly, leaving no residue. Once the system is activated, it’ll discharge in approximately ten seconds.”

“Can it be lethal?” Stone asked.

“If you hang around long enough and depending on the concentration levels of the flooding agent, you can suffer asphyxiation. It can also cause a heart attack.”

Stone looked triumphantly at Caleb.

“But the autopsy result said he suffered cardiopulmonary arrest,” Milton reminded him. “If he’d suffered a heart attack, the cause of death would’ve been listed as a myocardial infarction. A heart attack or a stroke leaves very clear physiological signs. The medical examiner wouldn’t have missed that.”

Stone nodded. “All right. But asphyxiation can happen, you said.”

“I don’t really think so,” Milton said. “Not after I spoke with Caleb earlier.”

“I looked more into the library’s halon system,” Caleb explained. “It’s rated as an NOAEL system. That stands for No Observed Adverse Effect Level, a standard protocol used in fire suppression. It relates to the cardio–sensitization levels present in a particular place in relation to the amount of flooding agent required to extinguish a fire. Bottom line, with a NOAEL level, you’d have plenty of time to escape the space before being affected. And even if the horn were disconnected for some reason, if the gas had come out of that nozzle, Jonathan would’ve heard it. There was no way halon could have incapacitated him so fast that he couldn’t have escaped.”

“Well, it looks like my theory on how Jonathan DeHaven died was incorrect,” Stone admitted. He looked up ahead. They had just pulled onto Good Fellow Street.

“Is that Vincent Pearl?” he asked.

Caleb nodded and said irritably, “He’s early, probably very eager to prove yours truly wrong about the Psalm Book.”

Reuben smirked. “I see he left the robes at home.”

“Keep your eyes open,” Stone warned as they got out of the car. “We are undoubtedly being watched.”

True to Stone’s words, the same pair of binoculars from the window across the street were trained on the group as they met Pearl and headed into the house. The person also had a camera and snapped a few shots of them.

Once inside, Stone suggested that the rare book dealer accompany Caleb to the vault alone. “It’s not that large of a space, and you two are the experts in the area,” he explained. “We’ll just wait upstairs for you.”

Caleb looked unhappily at Stone, doubtless for casting him solo to Pearl. For his part Pearl gazed at Stone suspiciously for a moment and then shrugged. “I doubt it will take me long to show that it is not a first–edition Psalm Book.”

“Take your time,” Stone called to them as the two men stepped onto the elevator.