“Well, specifically, it means that Mary may not be killed on January 7. In this timeline, she might be killed later. Worse, she might be killedearlier. While I cannot be sure, of course, I believe Constance has made one fatal error: she thinks she has two weeks in which to complete her plan of action. We can’t make that assumption. Mary, and everyone else for that matter, is in danger, because now that this time-pond has been so thoroughly disturbed, there is simply no way to predict what will happen.”

D’Agosta shook his head. “Constance is no dope. What do you think Leng suspects?”

“He can’t possibly suspect that Constance comes from the future—if he ever learned that, we would be lost. But here’s what I believe hedoesknow.” Pendergast held up his hand, spidery fingers rising one by one.

“One: He knows she’s no Duchess of Ironclaw.

“Two: He knows she’s prying into his life and already knows a great deal about it.

“Three: He will eventually notice, if he hasn’t already, the resemblance between Constance and Mary.

“Four: He will conclude that, because of her wealth and position in society—not to mention high intelligence—he must assume her interest in him is a threat, perhaps a grave one. Remember, Leng is pitiless and insouciantly destroys lives in ways you can’t imagine. If he feels threatened, his response will be ruthless and efficient.”

“What kind of response?”

“He is consummately clever, Vincent—there is no way to know how he’ll strike, or where, or when. That’s why I need your help. He might cripple or even kill Constance. Then again, he might just as well decide that this is a sporting proposition and allow her to play out her hand…for his own amusement, before striking her down.” Pendergast shook his head. “We simply do not know.”

“So where do I come in?”

“I need you to watch the house with minute attention. He’ll want to learn more about the mansion and its occupants, if he hasn’t already. He might even attempt a break-in to gain information. I want you to report back what you see—of him, or more likely his devilish assistant, Munck—without making yourself obvious.”

“That’s easy enough to say, but how are we going to get 24/7 coverage of her house? I can’t watch the place for days on end—and neither one of us has a cell phone.”

“I fear things are rushing to a head…and that we won’t have ‘days on end.’”

A knock came at the door and D’Agosta got up to answer it. A bellboy rolled in a trolley with a bottle of champagne stuffed into a silver bucket and a large tray of blinis piled with sour cream and caviar.

“Over here,” said Pendergast, gesturing.

The bellboy wheeled it over next to his chair, and Pendergast slid a hand into his pocket and extracted a silver dollar, languidly holding it out to the bellboy between two fingers.

“Thank you, sir!” the boy said, taking it with a smart bow and leaving.

“You may serve me,” said Pendergast. “It will give you good practice.”

With a chuckle, D’Agosta poured out two glasses of champagne, then slid a half-dozen blinis onto a small plate, retreating to his seat to leave Pendergast to get his own caviar. He stuffed two blinis in his mouth and took a swig of champagne. Damn, it was good—better than he remembered champagne ever tasting. Could there be something in the water, or the grapes, or even the soil they grew in, that had changed for the worse over the last century and a half?

Finally, D’Agosta broke the silence. “Do you know what Constance is planning to do?”

“I know what she told me, in the note she left behind. And I overheard her making a most unwise proposition to Leng. If she can manage to rescue Mary, her next act will be to kill Leng.”

D’Agosta stared. “Killthe man? Really? She’d go that far?”

Pendergast lowered his voice. “You know her almost as well as I do.”

D’Agosta nodded. He was right: of course she would want to kill him—and there’d be no stopping her.

“How is she going to do it?”

“She offered Leng some chemical formulae he’s desperate to acquire. She didn’t say what she wanted in return, but obviously she will demand that he turn over Mary, immediately—without giving him time to plan an effective countermove.”

“And then she’ll kill him?” D’Agosta repeated. “How?”

“She lacks a volcano to throw him into,” Pendergast said dryly. “But that stiletto of hers strikes as fast as a black mamba and is just as deadly if the victim is taken by surprise. But you see, Vincent, this time the victim willnotbe taken by surprise. Leng might well be one, even two steps ahead of her, and she’ll never get the opportunity to strike.”

“So what’s your plan?”

“I plan to—what is that useful baseball term?—shortstopher. Since Constance cannot be deterred, our only course of action is to rescue Mary ourselves.”