At the outset of the novel Sarah’s oblivious husband, Henry Miles, meets Maurice and confides to him that he believes his wife is cheating on him. Maurice is both amused and appalled at the irony of the situation, since Henry still had no clue that Maurice himself had been Sarah’s lover several years earlier. Maurice—more than he lets on—is as curious about Sarah’s new lover as Henry is and commissions a private detective to find out who he is. The end of Maurice and Sarah’s affair years before had hurt Maurice deeply, all the more because Sarah’s reasons for leaving him were largely unexplained. Maurice believes he hates Sarah for being so fickle, and hates Henry for being so oblivious.

Half-way through the novel, the perspective of the novel changes when the private investigator that Maurice hired delivers Sarah’s diary to him. In a series of entries, the diary reveals to Maurice that Sarah was not actually committing adultery with another lover, but had instead been traveling a long road to religious conversion. This new presence of faith in her life was in fact the reason why she had left Maurice several years before.

As the diary reveals, Sarah’s conversion began the same day that marked the end of her adultery with Maurice. That pivotal day was during war, when the German V-1 rockets first began to bombard London. Sarah had been spending the afternoon at Maurice’s apartment when one of the rockets landed nearby, burying Maurice under a pile of rubble. Sarah sees him, believes he is dead, and calls out to the God she had been fighting against for many years: “Let him be alive and I will believe.” Miraculously, after her prayer, Maurice walks through the door, very much alive. Sarah is shocked. Maurice remembers only waking up, as if he’d been asleep.

All Sarah’s actions after this point make no sense to Maurice, who cannot understand why she no longer wants to make love, nor why she begins to avoid him. The jealous Maurice is unaware of Sarah’s Luther-like vow to God, and ascribes the worst motives to her. Sarah, on the other hand, is frightened of her vow, and seeks out any possible way to avoid truly giving herself over to God. Later on the novel reveals that Sarah had been baptized as a child into the Roman Catholic church; God had His mark on her from the beginning, and had been hounding her from the beginning. Sarah tries to find a materialistic explanation for everything from a local rationalist with a deformed face and the passion of an evangelist, but instead finds her belief in the supernatural confirmed. She struggles and prays against God, but is at every turn confronted with His irresistible love for her, even in her weakness and inconstancy. She has tried to find something to maintain an independence from God, which she admits is an illusion. She prays:

All my life I’ve tried to live in that illusion—a soothing drug that allows me to forget that I’m a bitch and a fake. But what are you supposed to love then in the bitch and the fake? Where do you find that immortal soul they talked about? Where do you see this lovely thing in me—in me of all people? I can understand that you can find it in Henry—my Henry, I mean. He’s gentle and good and patient. You can find it in Maurice who thinks he hates, and loves, loves all the time. Even his enemies. But in this bitch and fake where do you find anything to love?

In her struggles against faith, she reacts violently against the fleshiness of God and His Church. She could love a “god” made of vapour. It is matter which repulses her. She wants to believe that “we have invented the resurrection of the body.” It is a mere “fairy-tale we tell each other for comfort.” But when she is drawn to enter a church for solitude and quiet, she notices the crucifix:

And of course on the altar there was a body too—such a familiar body, more familiar than Maurice’s, that it had never struck me before as a body with all the parts of a body, even the parts the loin-cloth concealed. I remembered one in a Spanish church I had visited with Henry, where the blood ran down in scarlet paint from the eyes and the hands. It had sickened me. Henry wanted me to admire the twelfth-century pillars, but I was sick and I wanted to get out into the open air. I thought, these people love cruelty. A vapour couldn’t shock you with blood and cries…. So today I looked at a material body on that material cross, and I wondered, how could the world have nailed a vapour there? A vapour of course felt no pain and no pleasure. It was only my superstition that imagined it could answer my prayers. Dear God, I had said. I should have said, Dear Vapour. I said I hate you, but can one hate a vapour? I could hate that figure on the Cross with its claim to my gratitude—“I’ve suffered this for you,” but a vapour…

Sarah does eventually embrace the love of God, and as a result knows she cannot return to her love for Maurice Bendrix. Her love for God is also very different from her love for her husband, which had always been passionless and domestic. The last few chapters of the novel take a startling hagiographic turn, as Sarah—and relics of her—have a healing power on those around her. The rationalistic evangelist with the deformed face is healed, as is a young child on his death bed, because of this new saint, former sinner, Sarah Miles. Maurice resists all these evidences, even after Sarah dies and her relics seem to have some sort of mysterious healing power. Confronted with the loss of the woman whom Maurice both hates and loves still, he prays to God:

It wasn’t You that “took,” I told the God I didn’t believe in, that imaginary God whom Sarah thought had saved my life (for what conceivable purpose?) and who had ruined even in his non-existence the only deep happiness I had ever experienced: oh no it wasn’t You that took, for that would have been magic and I believe in magic even less that I believe in You: magic in your cross, your resurrection of the body, your holy Catholic church, your communion of saints.

The end of the novel, even on multiple re-readings, acts like a punch in the gut:

I wrote at the start that this was a record of hate, and walking there beside Henry toward the evening glass of beer, I found the one prayer that seemed to serve the winter mood: O God, You’ve done enough, You’ve robbed me of enough, I’m too tired and old to learn to love, leave me alone for ever.

In many respects, this novel—like many of Greene’s works—is not a pleasant read, in the conventional sense. This ending, particularly, is bitter to taste and bitter in the stomach. At the same time, it is one of the starkest representations of the modern perception of grace that is contained in 20th century literature. For Greene, the reluctant Catholic, modern man hates grace, hates the body. He prefers “vapour” and disembodied reason. God must not be allowed to interfere in the course of human events. This is the exile of God to which Nietzsche referred more than half a century before.

It is very telling how many reviewers revolt at the ending of The End of the Affair, while loving the beginning sections. Michael Gorra expresses a common criticism of the novel:

The End of the Affair demands that we accept its miracles as an intrinsic part of its structure, and moreover that we accept them with something other than the sense of suspended disbelief with which we view the miracles of what’s now called magic realism…. We can entertain the possibility that a miracle has occurred so long—and only so long—as the novel also leaves us free to entertain the possibility that it hasn’t; only so long as the novel does not require us to take a position. The last chapters of The End of the Affair do not allow us that freedom. They try instead to enforce belief…

Perhaps unwittingly, Gorra finds himself very much in the place of Maurice Bendrix. It seems, in fact, that Greene intends the supernaturalism of the last part of the novel to drive this wedge between his readers. The presence of God and His grace has a very polarizing effect, certainly on Maurice and Sarah. God must be loved or hated. It is impossible, in the end to remain neutral in our allegiance; one may not be impartial toward God, nor His Church.