"I got to go," I tell Ruiz.

"What's up?"

"Maybe nothing."

Climbing the stairs, two at a time, I reach the incident room. DS Casey is on the radio organizing refreshments for the search teams that are still at the scene. I wait for him to finish.

"The CCTV footage from the Bingham festival-where will I find it?"

"It should be on the database," he says.

"Can you call it up?"

He logs me into the nearest terminal, linking me into the Police National Computer, a vast database containing the details of every known offender and "person of interest" in the UK: their names, nicknames, aliases, scars, tattoos, accents, shoe size, height, age, hair color, eye color, offence history, a.s.sociates and modus operandi. It also hosts the case files of active investigations, allowing detectives to cross-reference details and search for links.

The Bingham festival footage is catalogued in a dozen different ways. It was shot from a CCTV camera opposite the bus stop at the entrance to the village green. Twenty-eight seconds of recording show Piper and Natasha leaving the funfair, walking along a sideshow alley and turning out of the gate.

I open another file, this one containing a series of images taken by a photographer for the Oxford Mail. He shot mostly kids eating candyfloss and riding on the carousel, but one sequence near the dodgem cars shows Piper and Natasha standing in the background.

I zoom in on the girls, moving through the images frame by frame. Behind them, parked on the road, I can see a patrol car with a police officer standing alongside, leaning on the open door. The image is too blurred and distant to recognize a face, but the stance is familiar.

Another photograph comes to mind-the one of Natasha McBain outside Oxford Crown Court, being escorted through a hate-filled crowd by a court security officer. His face is hidden behind a raised forearm as he pushes people aside.

Thoughts are now splattering into my consciousness like fat drops of rain on a dry road. First one then another... snowmen, stationmasters, missing girls... The truth isn't a blinding light or a cold bucket of water in the face. It leaks into my consciousness one drop at a time.

Pushing back from the desk, I cross the incident room and take a corridor as far as the changing rooms. Each officer has a steel storage locker for his or her uniform and kit. I walk down the rows of lockers, looking at the numbers and initials.

The locker is secured with a combination padlock. I look for something heavy. The fire extinguisher is buckled against the wall. I pull it free, raise it above my shoulders and smash it against the padlock. The door buckles, the lock breaks. I'm looking at body armor, police boots and a reflective vest. Hanging at the back of the locker is a pair of white overalls with OxSAR sewn into the breast pocket. The trouser cuffs are stained with soot and I smell bleach on the fabric.

DS Casey is at the radio, listening to the police operation in North Oxford. The cars are getting closer, sealing off the street.

"I need to ask you something. When the chief constable cancelled all holiday leave and officers were recalled, did that include everyone?"

"Yeah."

"Where was Grievous yesterday?"

"I saw him at one of the roadblocks."

"Where?"

"On the Silo Road."

"What about today?"

"I haven't seen him. What's this about?"

I don't answer for a moment. And then: "What's his full name?"

"Pardon?"

"His name... his proper one."

"Brindle Hughes."

"What about his first name?"

"Gerald."

"Does anybody ever call him George?"

"Everybody calls him Grievous."

Sitting at the computer terminal, I type a new search looking for a witness statement. The screen refreshes. I scan the list. The statement is signed and dated by Probationary Constable Gerald Brindle Hughes. He describes being on patrol on the Sat.u.r.day night that the Bingham Girls disappeared. He saw two girls matching the descriptions of Piper Hadley and Natasha McBain leaving the funfair at approximately ten o'clock.

"Where does Grievous live?"

Casey looks up from the radio. "Why?"

"We have to find him."

Casey looks at me apprehensively. His hairline creeps closer to his eyes.

"What's he done?"

"I'm not sure, but I need you to trust me. If I'm right, it could make your career. If I'm wrong..."

I don't finish the sentence. Casey has grown nervous. "Maybe I should call the boss."

"Don't use the radio. He'll be listening."

"Who?"

"Grievous. That's how he found Piper."

"What are you talking about?"

"He's been monitoring the police radio messages. That's how he knew where to find Piper. He heard her location being given over the radio. He got there before anyone else."

"But how?"

"He knew where she escaped from."

The penny drops. Casey looks at me in disbelief. "Are we talking about the same person? Trainee Detective Constable Brindle Hughes?"

"I hope I'm wrong. Please, we have to hurry."

49.

DS Casey shoulders open the external fire door and points his keys at an unmarked police car. Lights flash and doors unlock.

"The boss's phone is turned off," he says, holding a mobile to his ear. "He won't turn it on until after the operation. It's procedure. Urgent comms only."

Casey stares at the screen, pondering whether to leave a message. He wants to cover himself.

"I'll explain it to DCI Drury," I say, sliding into the pa.s.senger seat.

Moments later we pull out of the parking area and accelerate along Marcham Road. The streets are deserted. People are indoors, celebrating Christmas, eating turkey and the tr.i.m.m.i.n.gs, plum pudding with custard, dozing off in front of the TV before the Queen makes her speech.

"I still can't believe we're doing this," says Casey. "Grievous is one of the lads."

"How well do you know him?"

"He's a mate."

"So you've been to his place?"

"No."

"Have you met his fiancee?"

"Not yet."

"She's never come to the pub for a drink or dropped Grievous at the station?"

"No." Casey falters. "He hasn't been with us long. Six months maybe."

"Where was he before that?"

"In uniform... working downstairs."

The DS swings hard into Drayton Road, past Ock Meadow, heading south, accelerating between intersections.

Facts are shifting in my head, detaching and re-forming into new pictures like the fragments of a montage, creating different realities. The past reshaped, history rewritten, explanations turned upside down.

Thinking out loud, I explain how Grievous was working the night that Piper and Natasha disappeared. The girls must have walked right past him as they headed for the leisure center. He was also working as a court security officer when they gave evidence against Aiden Foster at Oxford Crown Court.

"That could be just a coincidence," says Casey.

"Remember the farmhouse on the night of the blizzard? Augie Shaw said he saw Natasha on the road. Barefoot. Terrified. There was someone chasing her."

"The snowman," says Casey.

"I think it was someone dressed in white overalls, a search and rescue volunteer. Grievous works for OxSAR."

"A lot of guys work as volunteers."

"His overalls smell of bleach."

"Is that the best you have? Phillip Martinez has a motive and no alibi. The guy is a control freak, you said so yourself. He's got medical training. He could have done that stuff... you know... to Natasha."

Casey won't use the words.

"Grievous did two years of nursing before he became a court security officer."

"How do you know?"

"He told me."

"What about the figurine you found at the abandoned factory?"

"Grievous was with me when I went to see Phillip Martinez. He saw the model railway. He could have picked up the stationmaster and planted it to implicate Martinez."

"You're making him sound like a master criminal. He's a trainee detective constable, for Christ's sake."

"Humor me then. We'll knock on the door, say h.e.l.lo, wish him a Merry Christmas."

"Then what?"

"We'll leave. One drink. That's all."

The DS isn't convinced. I'm asking him to distrust a colleague, to break a special bond. Police officers look after each other and cover each other's backs. They socialize together and take holidays and marry into each other's families. They're comrades in arms, outsiders, hated until needed, undertakers to the living.

The raid in North Oxford has unfolded over the two-way radio. Police are going from floor to floor, searching the bas.e.m.e.nt for hidden tunnels and secret rooms.

We're getting close. Casey pulls over a hundred yards from the address. This is a newer part of Abingdon with two-story semi-detached houses, some with loft conversions and garages. The painted brick facades stand out brightly against the winter trees. Some have Christmas lights strung under the eaves or around the windows.

"So we're just going to say h.e.l.lo?" says Casey.

"Absolutely."

"And then we'll leave?"

"Of course."

"And you won't embarra.s.s me by mentioning any of your theories to Grievous?"

"No."

We walk through the gate and along the path. Casey rings the doorbell. n.o.body answers.