Favell proceeds to tell Colonel Julyan that he and Rebecca were lovers, that the two were planning to get married, and that Maxim killed her out of jealousy. However, Favell's obvious drunkenness inclines the Colonel to distrust his words; he demands to know if Favell has any proof of his accusations, any witnesses to back up what he says. After thinking a moment, Favell says to call Ben, the retarded man who lives near the beach. Remembering Ben's cryptic comments about a "dark lady" who "won't come back again," the heroine fears that Ben might indeed have witnessed the murder, and that he will testify accordingly. But Ben, clutching his cap and whimpering about being put in an asylum, says that he saw nothing, and denies ever having seen Favell before.
Colonel Julyan points out that Favell cannot even prove that he and Rebecca were lovers at all. "Can't I?" he smirks, and calls for Mrs. Danvers. The old housekeeper tells the magistrate that yes, Favell and Rebecca were having an affair--but her mistress never cared about him: "Lovemaking was a game with her, only a game," she repeats adamantly, threatening to become hysterical. Colonel Julyan attempts to extract more useful knowledge from her, asking if Rebecca had any motive for suicide at the time of her death. Mrs. Danvers dismisses the idea, but mentions that she still has Rebecca's engagement book, documenting where she went in London the day she died. The book is fetched, and it shows that Rebecca had an afternoon appointment with a man named Baker, who turns out to be a doctor, a woman's specialist. It is decided that the whole company, save for Mrs. Danvers, will journey to London and interview him tomorrow.
It seems to the heroine, and to Maxim, that at last they will be found out. Dr. Baker will surely testify that Rebecca was pregnant; with this disclosure, the law authorities will surely suspect that Maxim killed his wife out jealous rage (as he did). Maxim and the heroine spend the night together "like guilty lovers," and the next morning they arise early and drive to London, accompanied by a now-sober Favell and the Colonel. Dr. Baker meets with them, and goes back over his records until he finally remembers Rebecca: she came to him under an assumed name, he says, calling herself "Mrs. Danvers." He tells the group that she was suffering from an incurable disease, an inoperable cancer of some sort. She had asked for a truthful diagnosis, he says, and he gave her one, telling her that she had only a few months to live. Incidentally, Dr. Baker adds, her uterus was malformed, and she could never have had children.
Thus from Colonel Julyan's perspective the mystery is solved, for Rebecca did have a motive for suicide. However, he advises Maxim and the heroine to leave the region for the time being, to take a holiday on the Continent, perhaps, until the gossip dies down. Favell drives away, shaken, muttering about whether cancer is contagious. Together, Maxim and the heroine begin the long trip back to Manderley. Night falls, and they find an inn and stop for the evening; Maxim telephones the butler Frith, and learns that Mrs. Danvers has vanished. He becomes uncomfortable, and after he dinner he decides not to spend the night at the inn, but to drive straight through until morning. The heroine sleeps in the car, dreaming fitfully, and in her dream she goes to the mirror and sees Rebecca's face instead of her own. She awakens suddenly, and sits beside Maxim for the rest of the drive. At one point she believes that she has glimpsed the sunrise: an orange glow permeates the horizon. But the glow is coming from the west, from over the hills ahead of them. The couple comes over a ridgeline and looks down into the valley; before them lies Manderley, consumed by leaping flames.
The scene in Dr. Baker's office offers the book's second great plot twist, and serves as the novel's denouement. Both the heroine and the reader assume that Dr. Baker will reveal what Rebecca told Maxim that fateful night--that she was pregnant with Favell's child. But now we learn that Rebecca's statement to Maxim was merely another one of her many lies: indeed, perhaps this last deceit was even calculated to make Maxim kill her, and thereby to bring about his death when the murder was found out. Lastly, the fact that Rebecca was sterile resonates somewhat symbolically: just as no good can come of evil, so too can no child issue from Rebecca's womb.
The final pages of the novel see Maxim and the heroine driving home, apparently victorious. But Rebecca has taken the form of a flashback; the reader knows that in the book's "present," Manderley has burned. Thus we do not need the news of Mrs. Danvers's disappearance to warn us that trouble is awaiting the de Winters upon their return home. (While we never know for certain that Mrs. Danvers set the fire, all the signs point to such a conclusion.) And in a way, the burning of the house is the price the heroine and her husband must pay for their triumph over Rebecca: they have overcome her insidious power, but they have done so by murder and concealment, and they must answer for this.