Excerpt from The Stranger on the Train by Abbie Taylor, plus links to reviews, author biography & more

"Der," he said, thrilled, as the headlights lit up the tunnel. He let go of Emma's jeans to point. The grimy red, white and blue carriages roared into the station. Squeals and screeches filled the platform; the train slowed, then stopped. The roar of the engine died abruptly, like a turned-off fan.

Silence.

A second later, the doors whoomped open.

"On you go," Emma said.

Ritchie didn't need to be told twice. Emma steered him to an empty carriage, keeping his harness taut, lifting it a little to help him climb on board. He struggled in on his hands and knees, the top of his nappy sticking out from his cargo pants. Then he stood up again in the doorway, delighted with himself.

"Muh," he said, turning to wave her aboard with a fat hand.

That was how she saw him, mostly, in the weeks that followed. Standing there in the doorway with his toothy little grin, his crooked fringe, his blue fleece with the smiley elephant on the front. There was nothing different about him, nothing she hadn't seen a thousand times before. No whisper in her head warning her to snatch him back from the carriage and never let him go. He was still waving as she loaded the buggy on beside him and turned to pick up the bags. Reaching down, Emma thought she felt something with her other hand: a slight, sideways jerk on the harness she was gripping. Just a small thing, but looking back there must have been something odd about it, because she remembered frowning to herself. Even before she had a chance to straighten, to look, she knew that something was wrong.

Whoomp.

She spun around. For a second, she found it hard to take in what she was seeing. Her thoughts zigzagged. What is missing from this picture? She still held Ritchie's harness in her hand, but the door of the carriage was closed.

Closed in her face, and Ritchie was on the other side.

"Jesus!"

Dropping the bags, Emma sprang at the door and tried to get her fingers around the edges. Through the window, she saw the top of Ritchie's head.

"Hang on," she called. "I'm coming."

Oh God, how did you open the door? Everything was a blur. Then she found the "Open" button and pressed it. Nothing happened. She jabbed again, harder this time. Still nothing. She began to bang on the door with her fists.

"Help!" She looked wildly around the platform. "My baby's stuck."

Her voice rose thinly and trickled away. The platform was deserted. Just dark slabs of concrete, metal benches along the walls, the silent tunnels at each end.

"Shit." Emma's heart was pounding. She felt very quick, alert. She looked around again and this time spotted a red box on the wall with a glass panel on the front. The fire alarm. Instinctively she jerked towards it. Then she stopped. To reach the alarm, she would have to let go of Ritchie's harness. She dithered, unable to make herself relinquish, even for one second, her contact with her son.

"Help!" she yelled again, louder this time. "Somebody."

Surely someone must hear. This was a public place, for God's sake. She was right in the middle of London.

Something occurred to her then. The train hadn't moved. The doors seemed to have been closed for an age but the train was still just standing there.

"They know we're here." She sagged with relief. Of course. The train couldn't go while the harness was caught in the door. The driver could see her in a mirror or camera or something. Someone would be along in a minute to help. She stood there, waiting, not knowing what else to do. "It's all right," she told herself. "It's all right."

She looked in again to check on Ritchie. Then she jumped. What was that? That movement, way down at the end of the carriage?

Someone was in there. Someone was in there with Ritchie.

Excerpted from The Stranger on the Train by Abbie Taylor. Copyright © 2014 by Abbie Taylor. Excerpted by permission of Atria/Emily Bestler Books. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.