Jon Cartwright was stationed at the door beside him, a witchlight stone glowing in his hand. Time passed; they did their best to ignore each other.

“Too bad you can’t use one of these,” Jon said finally, holding up the stone. “Or one of these.” He tapped the seraph blade hanging from his belt. The students hadn’t been taught how to fight with them yet, but several of the Shadowhunter kids had brought their own weapons from home. “Don’t worry, hero. If the vamp shows up, I’m here to protect you.”

“Great, I can hide behind your massive ego.”

Jon wheeled on him. “You want to watch yourself, mundane. If you’re not careful, you’ll . . .” Jon’s voice trailed off. He backed up until he was pressed against the wall.

“I’ll what?” Simon prompted him.

Jon made a noise that sounded suspiciously like a whimper. His hand floundered at his belt, fingers stretching for the seraph blade but coming nowhere near it. His eyes were riveted on a spot just over Simon’s shoulder. “Do something!” he squeaked. “She’s going to get us!”

Simon had seen enough horror movies to get the picture. And the picture was enough to make him want to bolt for the door, slip through it into the daylight, and keep running until he was back home, doors locked, safely under the bed, where he’d once hidden from imaginary monsters.

Instead, slowly, he turned around.

The girl who melted out of the shadows looked to be about his age. Her brown hair was pulled back into a high ponytail, her glasses were dark pink and horn-rimmed vintage, and her T-shirt featured a bloody, crimson-shirted Star Trek officer and read, LIVE FAST, DIE RED. She was, in other words, exactly Simon’s type—except for the fangs glinting in his flashlight beam and the inhuman speed with which she streaked across the room and kicked Jon Cartwright in the head. He crumpled to the ground.

“And then there were two,” the girl said, and smirked.

It had never occurred to Simon that the vampire would be his age, or at least look it.

“You want to be careful with that thing, Daylighter,” she said. “I hear you’re alive again. Presumably you want to keep it that way.”

Simon looked down to realize he had taken the dagger into his hand.

“You going to let me out of here, or what?” she asked.

“You can’t go out there.”

“No?”

“Sunshine, remember? Makes vampires go poof?” Simon couldn’t believe his voice wasn’t shaking. Honestly, he couldn’t believe he hadn’t peed his pants. He was alone with a vampire. A cute, girl vampire . . . that he was supposed to kill. Somehow.

“Check your watch, Daylighter.”

“I don’t wear a watch,” Simon said. “And I’m not a Daylighter anymore.”

She stepped closer to him, close enough to stroke his face. Her finger was cold, her skin as smooth as marble. “Is it true you don’t remember?” she said, peering curiously at him. “You don’t even remember me?”

“Did I . . . do I know you?”

She brushed her fingertips across her lips. “The question is, how well did you know me, Daylighter? I’ll never tell.”

Clary and the others had said nothing about Simon having vampire friends, or . . . more-than-friends. Maybe they’d wanted to spare him the details of that part of his life, the part where he’d thirsted for blood and walked in the shadows. Maybe he’d been so embarrassed that he’d never told them.

Or maybe she was lying.

Simon hated this, the not knowing. It made him feel like he was walking on quicksand, every unanswered question, every new discovery about his past sucking him farther down into the muck.

“Let me go, Daylighter,” she whispered. “You would never have hurt one of your own.”

He’d read in the Codex that vampires had the ability to mesmerize; he knew he should be guarding himself against it. But her gaze was magnetic. He couldn’t look away.

“I can’t do that,” he said. “You broke the Law. You killed someone. Many someones.”

“How do you know?”

“Because . . .” He stopped, realizing how feeble it would sound: because someone told me so.

She guessed at the answer anyway. “You always do what you’re told, Daylighter? You never think for yourself?”

Simon’s hand tightened on the dagger. He’d been so worried about discovering he was a coward, too frightened to fight. But now that he was here, facing the supposed monster, he wasn’t afraid—he was reluctant.

Sed lex, dura lex.

Except maybe it wasn’t so simple; maybe she’d just made a mistake, or someone else had, maybe he’d gotten the wrong information. Maybe she was a cold-blooded killer—but even so, who was he to punish her?

She angled past him toward the door. Without thinking, Simon moved to block her. His dagger swung up, slicing a dangerous arc through the air and whistling past her ear. She danced backward, laughing as she lunged for him, fingers curled like claws. Simon felt it then, for the first time, the adrenaline surge he’d been promised, the clarity of battle. He stopped thinking in terms of techniques and moves, stopped thinking at all, and simply acted, blocking and ducking her attack, aiming a kick at her ankles to sweep her legs out from under her, slashing the dagger across pale skin, drawing blood, and as his mind kicked into gear again, a step behind his body, he thought, I’m doing it. I’m fighting. I’m winning.

Until she wrapped a hand around his wrist in an iron grip, flipped him over onto his back as if he were a small child, and straddled him. She’d been playing with him, he realized. Pretending to fight, until she got bored.

She lowered her face toward his, close enough that he would have felt her breath—if she’d been breathing.

He remembered, suddenly, how cold he had been, when he was dead. He remembered the stillness in his chest, where his heart no longer beat.

“I could give it all back to you, Daylighter,” she whispered. “Eternal life.”

He remembered the hunger, and the taste of blood.

“That wasn’t life,” he said.

“It wasn’t death, either.” Her lips were cold on his neck. Everything about her was cold. “I could kill you now, Daylighter. But I’m not going to. I’m not a monster. No matter what they told you.”

“I told you, I’m not a Daylighter anymore.” Simon didn’t know why he was arguing with her, especially now, but it seemed important to say it out loud, that he was alive, that he was human, that his heart beat again. Especially now.

“You were a Downworlder once,” she said, rising over him. “That will always be a part of you. Even if you forget, they never will.”

Simon was about to argue, again, when a shining whip lashed out of the shadows and wrapped around the girl’s neck. It yanked her off her feet and she landed hard, head cracking against the cement floor.

“Isabelle?” Simon said in confusion, as Isabelle Lightwood charged at the vampire, blade gleaming.

He’d never before realized what a horrible crime against nature it was that he had lost his memories of Isabelle in action. It was clear that it was her natural state. Isabelle standing still was beautiful; Isabelle leaping through the air, carving death into cold flesh, was unworldly, burning as brightly as her golden whip. She was like a goddess, Simon thought, and then silently corrected himself—she was like an avenging angel, her vengeance swift and deadly. Before he could lever himself off the ground, the vampire girl’s throat was split wide open, her undead eyes rolling back in her head, and like that, it was over. She was dust; she was gone.

“You’re welcome.” Isabelle extended her hand.

Simon ignored it, rising to his feet without her help. “Why did you do that?”

“Um, because she was about to kill you?”

“No, she wasn’t,” he said coldly.

Isabelle gaped at him. “You’re not seriously mad at me? For saving your ass?”

It wasn’t until she asked that he realized he was. Angry at her for killing the vampire girl, angry at her for assuming he needed his ass saved and being pretty much right, angry at her for hiding in the dark, waiting to save him, even though he’d made it painfully clear that there couldn’t be anything between them anymore. Angry that she was a supernaturally sexy, raven-haired warrior goddess and apparently against all odds still in love with him—and he was apparently going to have to break up with her, again.