Excerpt from Sweet Tooth by Ian McEwan, plus links to reviews, author biography & more

The DI switches off the projector and turns up the lights. His manner is apologetic. They could have prosecuted, he says. Wasting police time, perverting the course of justice, that sort of thing. But clearly this is a delicate domestic matter and Sebastian will have to decide for himself what to do. The two men go down the stairs and out into the street. As he shakes Sebastian's hand the DI says he is terribly sorry, he can see that this is a difficult situation and he wishes him all the best with it. Then, before he goes back into the station, he adds that it was the view of the police team working in the shop, who had recordings of what was said at the counter, that "Mrs. Morel probably needed help."

On the way home—has he ever walked more slowly?—he would have stopped in that same pub for another fortifying drink, but he does not have on him even the price of a half pint. Perhaps it's just as well. He needs a clear head and clean breath. It takes him an hour to walk the mile to his house.

She is cooking with the children when he comes in. He lingers in the doorway of the kitchen watching his little family at work on a cake. It was terribly sad, the way Jake and Naomi's precious heads bobbed so eagerly at their mother's murmured instructions. He goes upstairs and lies on the bed in the spare room, staring at the ceiling. He feels heavy and tired and wonders if he is suffering from shock. And yet, despite the awful truth he has learned that day, he is troubled now by something new and equally shocking. Shocking? Is that the right word?

When he was downstairs just now watching Monica and the children, there was a moment when she glanced back over her shoulder at him. Their eyes met. He knows her well enough, he has seen that look many times before and has always welcomed it. It promises much. It is a tacit suggestion that when the moment is right, when the children are asleep, they should seize their chance and obliterate all thoughts of domestic duties. In the new circumstances, with what he knows now, he should be repelled. But he is excited by that glance because it came from a stranger, from a woman he knows nothing about beyond her obvious taste for destruction. He had seen her in a silent movie and realized that he had never understood her. He had got her all wrong. She was no longer his familiar. In the kitchen he had seen her with fresh eyes and realized, as though for the first time, how beautiful she was. Beautiful and mad. Here was someone he had just met, at a party say, noticed her across a crowded room, the sort of woman who, with a single unambiguous look, offers a dangerous and thrilling invitation.

He has been doggedly faithful throughout his marriage. His fidelity now seems like one more aspect of the general constriction and failure in his life. His marriage is over, there can be no going back, for how can he live with her now? How can he trust a woman who has stolen from him and lied? It's over. But here is the chance of an affair. An affair with madness. If she needs help, then this is what he can offer.

That evening he plays with the children, cleans the hamster's cage with them, gets them into their pajamas, and reads to them three times over, once together, then to Jake on his own, then to Naomi. It is at times like these that his life makes sense. How soothing it is, the scent of clean bed linen and minty toothpaste breath, and his children's eagerness to hear the adventures of imaginary beings, and how touching, to watch the children's eyes grow heavy as they struggle to hang on to the priceless last minutes of their day, and finally fail. All the while he is aware of Monica moving about downstairs, he hears the distinctive clunk of the oven door a few times and is aroused by the simple distracting logic: if there is to be food, if they are eating together, then there will be sex.

When he goes down, their tiny sitting room has been tidied, the usual junk has been cleared from the dining table and there is candlelight, Art Blakey on the hi-fi, a bottle of wine on the table and a roast chicken in an earthenware dish. When he remembered the police film—his thoughts kept returning to it—he hated her. And when she came in from the kitchen in fresh skirt and blouse, bearing two wineglasses, he wanted her. What is missing now is the love, or the guilty memory of love, or the need for it, and that is a liberation. She has become another woman, devious, deceitful, unkind, even cruel, and he is about to make love to her.

Excerpted from Sweet Tooth by Ian McEwan. Copyright © 2012 by Ian McEwan. Excerpted by permission of Nan A. Talese. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.