Mutualism: symbiosis with mutual advantage to both or all organisms involved.

The word that defined Warren Hoyt’s pact with his new partner. The Surgeon and the Dominator, working as a team. Hunting and feeding off carrion together.

“Warren Hoyt has always worked best with a partner,” said Dr. Zucker. “It’s how he likes to hunt. The way he used to hunt with Andrew Capra, until Capra’s death. Indeed, Hoyt requires the participation of another man as part of his ritual.”

“But he was hunting on his own last year,” said Barry Frost. “He didn’t have a partner then.”

“In a way, he did,” said Zucker. “Think about the victims he chose, here in Boston. All of them were women who’d been sexually assaulted-not by Hoyt, but by other men. He’s attracted to damaged women, women who’ve been marked by rape. In his eyes, that made them dirty, contaminated. And therefore approachable. Deep down, Hoyt is afraid of normal women, and his fear makes him impotent. He can only feel empowered when he thinks of them as inferior. Symbolically destroyed. When he hunted with Capra, it was Capra who assaulted the women. Only then did Hoyt use his scalpel. Only then could he derive full satisfaction from the ritual that followed.” Zucker looked around the room and saw heads nodding. These were details that the cops in this room already knew. Except for Dean, they had all worked on the Surgeon investigation; they were all familiar with Warren Hoyt’s handiwork.

Zucker opened a file folder on the table. “Now we come to our second killer. The Dominator. His ritual is almost a mirror image of Warren Hoyt’s. He’s not afraid of women. Nor is he afraid of men. In fact, he chooses to attack women who live with male partners. It isn’t just a matter of the husband or boyfriend being inconveniently present. No, the Dominator seems to want the man there, and he goes in prepared to deal with him. A stun gun and duct tape to immobilize the husband. The positioning of the male victim so he’s forced to watch what happens next. The Dominator doesn’t just kill the man straightaway, which would be the practical move. He gets his thrills by having an audience. By knowing another man is there to watch him claim his prize.”

“And Warren Hoyt gets his thrills by watching,” said Rizzoli.

Zucker nodded. “Exactly. One killer likes to perform. One likes to watch. It’s a perfect example of mutualism. These two men are natural partners. Their cravings complement each other. Together, they’re more effective. They can better control their prey. They can combine their skills. Even while Hoyt was still in prison, the Dominator was copying Hoyt’s techniques. He was already borrowing elements from the Surgeon’s signature.”

This was a point Rizzoli had recognized before anyone else, but no one in the room acknowledged that particular detail. Perhaps they’d forgotten, but she hadn’t.

“We know Hoyt received a number of letters from the general public. Even from prison, he managed to recruit an admirer. He cultivated him, maybe even instructed him.”

“An apprentice,” said Rizzoli softly.

Zucker looked at her. “That’s an interesting word you use. Apprentice. Someone who acquires a skill or craft under the tutelage of a master. In this case, it’s the craft of the hunt.”

“But which one is the apprentice?” said Dean. “And which one is the master?”

Dean’s question unnerved Rizzoli. For the past year, Warren Hoyt had represented the worst evil she could imagine. In a world where hunters stalked, none could match him. Now Dean had brought up a possibility she didn’t want to consider: that the Surgeon was but an acolyte to someone even more monstrous.

“Whatever their relationship,” said Zucker, “they are far more effective as a team than as individuals. And as a team, it’s possible the pattern of their attacks will change.”

“How so?” asked Sleeper.

“Until now, the Dominator has chosen couples. He props up the man as his audience, someone to watch the assault. He wants another man there, to see him claim the prize.”

“But now he has a partner,” said Rizzoli. “A man who’ll watch. A man who wants to watch.”

Zucker nodded. “Hoyt just might fill the pivotal role in the Dominator’s fantasy. The watcher. The audience.”

“Which means he may not choose a couple next time,” she said. “He’d choose…” She stopped, not wanting to finish the thought.

But Zucker was waiting to hear her answer, an answer he had already arrived at. He sat with head cocked, pale eyes watching her with eerie intensity.

It was Dean who said it. “They’ll choose a woman, living alone,” he said.

Zucker nodded. “Easy to subdue, easy to control. With no husband to worry about, they can focus all their attention on the woman.”

My car. My home. Me.

Rizzoli pulled into a parking space at Pilgrim Hospital and turned off the ignition. For a moment she did not step out of the car but sat with doors locked, scanning the garage. As a cop, she’d always considered herself a warrior, a hunter. Never had she thought of herself as prey. But now she found herself behaving as prey, wary as a rabbit preparing to leave the safety of its den. She, who had always been fearless, was reduced to casting nervous glances out her car window. She, who had kicked down doors, who’d always joined the first wave of cops barreling into a suspect’s home. She caught a glimpse of herself in the rearview mirror and saw the wan face, the haunted eyes, of a woman she scarcely knew. Not a conqueror, but a victim. A woman she despised.

She shoved open the door and stepped out. Stood straight, reassured by the weight of her weapon, holstered snugly at her hip. Let the bastards come; she was ready for them.

She rode alone in the garage elevator, shoulders squared, pride trumping fear. When she stepped off again, she saw other people, and now her weapon felt unnecessary, even excessive. She tugged down her suit jacket to keep the holster concealed as she walked into the hospital, and stepped into the elevator, joining a trio of fresh-faced medical students with stethoscopes poking out of their pockets. They traded medical-speak among themselves, showing off their freshly minted vocabulary, ignoring the tired-looking woman standing beside them. Yes, the one with the concealed weapon on her hip.

In the ICU, she walked straight past the ward clerk’s desk and headed to cubicle #5. There she halted, frowning through the glass partition.

A woman was lying in Korsak’s bed.

“Excuse me. Ma’am?” a nurse said. “Visitors need to check in.”

Rizzoli turned. “Where is he?”

“Who?”

“Vince Korsak. He should be in that bed.”

“I’m sorry; I came on duty at three-”

“You were supposed to call me if anything happened!”

By now, her agitation had attracted the attention of another nurse who quickly intervened, speaking in the soothing tones of one who has dealt often with upset relatives.

“Mr. Korsak was extubated this morning, ma’am.”

“What do you mean?”

“The tube in his throat-the one to help him breathe-we took it out. He’s doing fine now, so we transferred him to the intermediate care unit, down the hall.” She added, in defense: “We did call Mr. Korsak’s wife, you know.”

Rizzoli thought of Diane Korsak and her vacant eyes and wondered if the phone call had even registered, or if the information had simply dropped like a penny into a dark well.

By the time she reached Korsak’s room, she was calmer and back in control. Quietly she poked her head inside.

He was awake and staring at the ceiling. His belly bulged beneath the sheets. His arms lay perfectly still at his sides, as though he was afraid to move them lest he disturb the tangle of wires and tubes.