They were half a block ahead of her, unaware that she was following them, although she was staring so fiercely surely they could feel the heat of her gaze on their backs. Who was that girl with Liam? How long had this been going on between them? It was obvious that something was going on, just by the way he draped his arm over her shoulders, by the way their heads tipped together. In her high-heeled boots, she was almost as tall as he was, and the cinched belt of her down jacket emphasized a model-thin waist and slim hips. Tight blue jeans showed off impossibly long legs.

Her stomach churned, and suddenly she felt so sick she reeled against a streetlamp and retched into the gutter, vomiting up sour-tasting water. For a moment, all she could do was hang on to that icy pole as people passed by her. No one asked if she was okay. No one stopped to offer a kind word. Though surrounded by pedestrians and traffic, she was all alone, invisible.

When at last she lifted her head, Liam and the dark-haired slut were nowhere to be seen.

It was only a ten-minute walk to Liam’s off-campus apartment. When she arrived and rang his buzzer, no one answered. She let herself into 2D to wait for him.

The instant she stepped into his apartment, she sensed there was something different in the air—the way it smelled, the way the molecules themselves seemed statically charged as they swirled around her. What had once belonged to her was now foreign terrain, claimed by a usurper, and she’d been blind to what was now so obvious. She remembered the alien cartons of yogurt she’d seen in his refrigerator, the Stanford Law School brochure in his stack of mail, and the fact his bed had been so neatly made. It was her doing. The Bitch. She’d managed to slither her way into her territory, and Taryn had missed all the signs.

She sat on the sofa facing the bookcase, where the photo of Liam and herself used to be. Instead of their picture was a small crystal globe, something she didn’t recognize. It caught the wintry light from the window, and she couldn’t stop staring at it. Yet another item that did not belong there.

Her hands were numb from the cold. From the shock. She tucked them inside her jacket and hugged herself. There was no one else here to hug her because Liam was now hugging someone else.

All afternoon and into the evening, she waited for him. She heard his neighbors on the second floor come home: The Abernathys returning from their boring jobs back to their boring lives. The blondes, giggling and chattering as they jangled keys. And from across the hall came the clang of virtual swordsmen in combat as the geeky grad students battled it out in some video game. But here in Liam’s apartment, there was only silence.

She didn’t remember falling asleep. She only knew that when she woke up on the sofa, it was dark, the building was silent, and her cell phone battery was down to 6 percent. It was exactly 4:45 a.m., and he’d never come home.

He was with her, of course. Staying with her. Sleeping with her.

She left Liam’s building and walked through the bitterly cold darkness to her apartment. She passed a twenty-four-hour coffee shop and smelled fresh-baked croissants, but she had no appetite, even though she hadn’t eaten a thing since yesterday. It seemed like a lifetime ago. A time when she’d thought Liam was still hers.

Before the Bitch had stolen him away.

By the time she reached her apartment, she was so chilled she didn’t even bother to undress but just pulled off her boots and crawled into bed, shivering. Thinking about Liam and her. This was the first time in all their years together that he’d strayed. This new girl was new to him, alluring only because she was fresh meat, and he didn’t yet know her flaws. Everyone had secrets, and surely she did too. A shoplifting arrest? An abortion? A boyfriend she’d cheated on? If she had any secrets at all, Taryn would ferret them out.

And she knew just the person who would help her.

“I don’t want to do it,” Cody said.

They were sitting in the student union food court, and as usual he’d loaded up his lunch tray with all the things he shouldn’t be eating: three slices of pizza, an order of french fries, and an extra-large Pepsi. There was no green vegetable in sight, unless you counted the flecks of bell pepper trapped in the congealing mozzarella. Taryn sat across from him, nursing only a cup of coffee because she was too keyed up to eat anything, and she was so frustrated by Cody’s intransigence that she wanted to shove his tray off the table, just to force him to look at her.

“I’m not asking you for a lot,” she told him.

“You’re asking me to spy on some girl I don’t even know.”

“That’s why you have to be the one to do it.”

“Why don’t you?”

“Because Liam might spot me. But he doesn’t know you. You can follow them anywhere, and you’ll never be noticed.”

“Now you want me to follow them too?”

“It’s the only way to know what they’re up to. You’re the one who’s seen all those Jason Bourne movies. This is exactly what spies do. They blend into the crowd and become as invisible as ghosts. You’ll be my personal secret agent.” She leaned forward, her voice dropping to an intimate whisper. He was looking right at her now. His mouth might be full of pizza, but all his attention was on her. She saw the glint of excitement in his eyes at the thought of Cody Atwood, secret agent. He was no Jason Bourne, but he was all she had.

“What do you want me to do?”

“Find out who she is. Her name, her hometown, whether she lives on campus or off. Find out her secrets.”

“How am I supposed to do that?”

“You’re the spy. You should know what to do.”

He was silent for a moment, rubbing a greasy hand on his chin as he mulled over how his hero Jason Bourne would handle the assignment. “I guess you’ll want photos,” he said. “I can dust off my Canon.”

“Great.”

“And I’ll need my telephoto lens.”

“You have one?”

“My grandpa gave me his old lens a few years ago. Haven’t used it in a while, but I’ll dig it out. So how do I find this girl? You haven’t even told me her name. Where do I look for her?”

“Begin with Liam.”

He sighed and sank back in his chair. In that instant she knew she was losing him and she’d have to do something quick to reel him back.

She put her hand on his arm. “You’re the only one I can count on, Cody.”

“It’s not really about the girl, is it? It’s still about Liam.”

“I need to know what she’s up to. What she’s planning.”

“Why?”

“Because I don’t trust her. And I need to look out for my friends.”

“By spying on him? On her?”

“I’d do it for you too. If I thought you were tangled up with the wrong person, I’d step in to protect you.”

“You would?”

“It’s what friends do. We watch out for each other.” And she truly meant it. She might not be in love with Cody or attracted to him, but she would never let anyone hurt him. It was a matter of loyalty.

“What if they catch me spying on them? I could get in trouble.”

“You’re too smart. I’m sure you’ll be good at this.”

He perked up, her chubby-cheeked Jason Bourne with a grease-smeared chin. “You really think so?”

“I know so.”

He sat up straighter. Took a deep breath. “So where do I find Liam?”

Her name was Elizabeth Whaley, and she lived in an apartment building two blocks from campus.

Cody turned out to be a better spy than Taryn had expected, and in only two days, he’d tracked down the girl’s apartment. It was a building that Taryn had walked past many times before, never imagining that this was where her enemy lived. The building was new, with underground parking, which meant the girl had money. That would impress Liam, and it would impress his parents even more. The girl was thin, fashionable, and rich.

There had to be something wrong with her.

Taryn waited across the street from the building until she saw a young man carrying a sack of groceries climb the steps to the front door. As he let himself in, she was right behind him, and they both stepped inside. No one ever felt threatened by a pretty girl, certainly not a girl who was smiling at them. He smiled back at her as they both got into the elevator, which quickly filled with the scent of green onions and cilantro from his sack of groceries. On the third floor he stepped off, but she stayed on until the fourth floor.

It was her floor. The enemy’s.

Taryn paused outside 405, listening. She heard no voices, no music, no sounds of anyone at home. But she was not planning to knock on that door anyway; instead, she knocked at 407, where the sound of a TV told her the occupant was at home.

A bedraggled woman wearing blue jeans answered the door. Her blonde hair was uncombed, and her eyes were hollow with fatigue. Somewhere in the apartment, a baby started crying. The woman glanced toward the sound, then looked back at her visitor.

“I’m sorry to bother you,” said Taryn. “Do you happen to know your neighbor very well? The one next door?”

“You mean Libby?”

Libby. Short for Elizabeth. “Yes,” said Taryn.

“I run into her once in a while. Say hello in the elevator. Why?”

“Have you had any, um, concerns about her?”

“You mean like noise?”

“Or other things.”

The baby cried louder. “Excuse me,” the woman said and ran into a bedroom. She returned holding the baby, who fussed and squirmed in her arms. As she jiggled it, she asked: “Is there some sort of problem with Libby?”