Ruiz is standing in the front garden, peering through a window. He cups his hands against the gla.s.s, letting his eyes adjust.

"Can you see anything?"

"Something is broken on the kitchen floor," he says.

"What is it?"

"A vase or maybe a plate."

"Accidental?"

"Maybe."

Dale Hadley is waiting in the car. Ruiz walks back to the main door. "Do you know the difference between reasonable suspicion and probable cause?"

"Not really."

"Reasonable suspicion is where a reasonable person suspects that a crime has been committed or is in the process of being committed. Probable cause is when a reasonable person believes that a crime is being committed or about to be committed. You see the difference?"

"Sort of."

"Good. Explain it to me later."

Pivoting on one foot, he hammers the lock with the heel of his boot. Wood splinters. The door swings open, banging on its hinges. He moves through the open-plan living room, yelling Emily's name. Broken crockery litters the kitchen floor. Thrown, not dropped.

Ruiz searches downstairs and I take upstairs. Emily's room is on the right side of the landing. Her bed is unmade and clothes are spilling from drawers. It contrasts starkly with the rest of the house, which is ordered and neat.

The untidiness is probably teenage-induced-I have one of them at home-although Emily didn't strike me as being as sullen and disorganized as Charlie. Pages have been torn from one of her schoolbooks. A train timetable lies in the wastepaper bin.

Opening the topmost drawer, I see a picture frame resting upside down beneath a folder. It's a woman's portrait. Pretty and smiling, she has long hair and familiar eyes: Emily's mother.

Ruiz yells from downstairs. I follow the sound of his voice to the garage. He's discovered the model railway and is grinning like a schoolboy.

"How cool is this?"

"Don't you mean nerdish?"

"Come on, didn't you ever want to be a train driver?"

"No."

"Let me guess-you grew up wanting to be a psychologist?"

"What's wrong with that?"

"You were one sad, sad child."

My mobile shudders to life. I flip it open.

"We've triangulated the signal," says Drury. "Piper's call came from a heavily wooded area half a mile north of the conference center, east of the Thames. The margin for error is about two hundred yards because the trees could be skewing the signal. I'm heading there now." He yells at someone to hold the lift. "Where are you?"

"At the Martinez house." I glance at Ruiz. "Emily Martinez didn't turn up for work today and there are broken dishes in the kitchen. You might want to send a forensic team."

"Where is Phillip Martinez?"

"He's not here."

There is a pause. Drury has stopped walking. "What should I know, Professor?"

"Piper said that George had a photograph of Emily in his wallet."

"And you think Phillip Martinez?"

"I think we're talking about the same person."

"Why didn't Piper say that?"

"I doubt that she's ever met Phillip Martinez or knows what he looks like. Martinez didn't move to Abingdon until after the divorce. He fought for custody after his wife's breakdown."

"Why would he kidnap Piper and Natasha?"

"He spent two years fighting for custody of Emily. He wasn't going to let someone take her away. He treats her like a possession. Like he owns her."

"But you said-"

"He matches the profile. He's a control freak. He has medical training. He was also at the house when Piper turned up on the last night of the festival. He could have overheard her talking to Emily. That's how he knew they were planning to run away."

"You said the kidnapping was most likely organized in advance."

"I said he targeted the girls for a reason. It wasn't random."

"What about the letters that were sent to Emily and Aiden Foster?"

"Martinez could have organized it. He expected the letters to be given to the police-to throw you off the trail."

"But he brought Emily's letter to the station."

"It was a fishing exercise. He wanted to find out how much you knew."

I can hear Drury breathing down the phone. He cups the receiver and yells down the corridor. "Put out a missing person's bulletin on Emily Martinez."

It's dark.

I can keep to the road by feeling the hardness of the dirt beneath my shoes, but I can't avoid the puddles. The rain has eased, but in the distance I can see shimmerings of lightning above the trees, followed by a dull rumbling.

The phone is still in my pocket. I can feel it with my fingers as I walk. I take it out, turn it over and feel for the catch to the battery compartment. The rear panel slides off and I use my thumbnail to lever the battery from its slot, before putting it back in again and replacing the panel.

I turn the phone on again. The screen lights up.

I call the last number.

"Daddy?"

"Piper! Thank G.o.d! We were worried."

"I dropped the phone. My hands were so cold."

"Are you OK? Where are you?"

"Are the police coming?"

"Yes. Where are you?"

"On a dirt road."

"Can you see any lights?"

"No. Tell them to hurry."

"I will."

"Have they found Tash?"

Daddy doesn't answer. Joe takes the phone.

"What's wrong?" I ask.

"Your dad needs a minute. He's a little overwhelmed. I need to ask you some questions."

"OK."

"Have you walked very far since we last spoke?"

"It feels like a long way because my feet hurt, but I don't think it is."

"Where are you now?"

"I'm on a dirt road. I pa.s.sed an old house and a barn, but n.o.body lives there."

"OK, just hold on, I'm going to relay that information to the police."

I can hear him talking to someone.

"OK, Piper, what else can you see from the road?"

"Nothing now, it's too dark. Before there was a pylon in a field."

"Have you seen the river?"

"No."

"What about a railway line?"

"I used to hear trains when I was in the bas.e.m.e.nt."

"That's good information, Piper. One more thing-have you ever met Emily's father?"

"No."

"Do you know what he looks like?"

"No. Why?"

"The man you call George-had you ever seen him before?"

"I don't think so. He knew stuff about us. He knew we'd given evidence in Aiden Foster's trial. He knew that Daddy worked in the City and that Tash's dad had been to prison."

"Is that all?"

"Uh-huh. I'm getting tired, Joe. My feet hurt. Do you think I could sit down for a while?"

Piper's body is closing down. Her words are getting slower and thicker. I turn to Ruiz. "Where are they?"

He relays the question to Drury, who's on the phone. "How close?"

Ruiz gives me the thumbs up. "They know the road. Cars are on their way."

"Did you hear that, Piper? They're close. Just a few more minutes."

"Mmmmm," she says.

"Keep talking, Piper... are you still there?"

"Uh-huh."

"I have a daughter about your age."

"What's her name?"

"Charlie."

"Where does she go to school?"

"Shepparton Park School-it's on the outskirts of Bath."