He hesitated, struggling to assemble the story in his mind. “We were under a carousel. Theo was already gone. The smokes were coming, I thought it was all over. Then she … climbed on top of me.”

“She climbed on top of you.”

He nodded. “Yes, on my back. Like she was shielding me. I know I’m not telling it right, but that’s how it happened. Next thing I knew, the smokes were gone. She led me to a hallway and showed me the stairs that led to the roof. That’s how I got out.”

For a moment Sara said nothing.

“I know it sounds strange.”

“Peter, why didn’t you tell anyone?”

He shrugged, at a loss. He had no defense, at least not a good one. “I should have. I wasn’t even sure the whole thing had actually happened. And once I didn’t say anything, it became harder and harder to actually do it.”

“What if Sanjay finds out?”

The girl had inched her face above the barricade of her knees; she appeared to be studying him, probing his face with a dark and knowing look. The feeling of wildness was still there, an animal jitteriness in the way she moved and held herself. But in the few minutes since they had entered the ward, a shift had occurred, a perceptible lessening of fear.

“He’s not going to,” Peter said.

“Oh my God,” a voice behind them said. “It’s true.”

They all turned to see Michael standing at the curtain.

“Circuit, how did you get in here?” Alicia hissed. “And keep your voice down.”

“Same as you. I saw the two of you going down the alley.” Michael moved cautiously toward the cot, his eyes locked on the girl. He was clutching something in his hand. “Seriously, who is that?”

“We don’t know,” Sara said. “She’s a Walker.”

For a moment Michael fell silent, his expression unreadable. Yet Peter could detect the workings of his mind, the swift calculations. He seemed, all of a sudden, to take notice of the object he was carrying.

“Holy shit. Holy shit. It’s just like Elton said.”

“What are you talking about?”

“The signal. The ghost signal.” He shushed them with a hand. “No, wait … hang on. I can’t believe this. Everybody ready?” His face lit up with a triumphant smile. “Here it comes.”

And just like that, the device began to buzz.

“Circuit,” said Alicia, “what the hell is that?”

He held it up to show them. A handheld.

“That’s what I came to tell you,” Michael said. “That girl? The Walker? She’s calling us.”

The transmitter had to be somewhere on her person, Michael explained. He couldn’t say exactly what it would look like. Large enough to have a power source, but beyond that he couldn’t say.