The final reveal of Dorothy Nicolson’s secret succeeds due to Morton’s careful plotting and structure. In creating two plausible scenarios for what happened between Dolly and Vivien during the war that each incorporate the details that Laurel has uncovered as well as the curated details given from the past, Morton builds suspense for the climactic shift from Laurel’s theory (Dorothy as a reformed Dolly) to the truth (Dorothy as Vivien). The twist succeeds because each of the conclusions that Laurel has drawn between Dorothy and Dolly, upon a second read, also work between Dorothy and Vivien. Laurel originally assumes Dorothy misses her family in Coventry who were killed in the Blitz, that she regrets trying to hurt Vivien Jenkins, and that her second chance came after Jimmy was killed, which inspired changes in her for the better. Through Laurel, Morton leads the reader to believe that Dorothy was protecting herself from a vengeful Henry Jenkins in 1961, casting her actions in a sympathetic light. When Dorothy is revealed to be Vivien, all the plot details remain consistent—Dorothy misses her family who was killed in a car accident in Australia, she regrets that Dolly died during the Blitz, and her second chance came after Dolly was killed. As Vivien, Dorothy’s murder of Henry Jenkins is cast in an even more sympathetic light—as self-defense against an abusive and vengeful husband.

Morton’s use of the dual timeline allows Laurel’s surprise discovery in the present to be immediately explained and contextualized by the past. As soon as Vivien boards Dolly’s train, Morton moves to calling her protagonist Dorothy, reaffirming her new identity. Throughout the book, Laurel’s mother has been called Dorothy, while Dolly refers to the young woman who grew up in Coventry, wanted to marry Jimmy, worked for Lady Gwendolyn, and imagined she was friends with Vivien. In calling older Vivien “Dorothy,” Morton confirms that this character is the mother Laurel loved and always believed her to be, the matriarch of the Nicolson family.

The two timelines also work together to provide answers as to what happened to Jimmy. Not only did Vivien escape Henry Jenkins, but Jimmy did as well—ironically, being conscripted from prison saved his life, taking Jimmy beyond the reach of Henry’s hired killers. It’s a more crushing irony that Dolly, who was so sure she had a glittering fate in store for her, who felt exhilarated walking the cratered streets of London during the Blitz, should be killed by a bomb after all. The twist is as cruel and unanticipated as the other bombs that destroyed her life: the one that killed her family in Coventry, and the one that allowed the blackmail letter to surface and be mailed, setting in motion the events that would take Dolly’s life and give Vivien a new one. Sealing the appropriation of her identity, Vivien takes Dolly’s fur coat, which holds the copy of Peter Pan that Dolly pretended Vivien dedicated to her, as well as the photograph of the two young women that Jimmy took at the play—further bits of evidence employed by Morton to connect Dolly Smitham and Dorothy Nicolson all along.

In revisiting the perspective of young Laurel in the concluding chapter, Morton lands at her final reveal that both Jimmy and Vivien have found their own ways of Surviving War and Trauma. The mysterious thank-you card that Laurel finds is revealed to be from Jimmy, who inherited Vivien’s old house on Campden Grove from his father (to whom Vivien bequeathed it). Closing with young Laurel brings the novel full circle, since it opened with young Laurel at eight years old, the same age that Vivien was when her family died and her journey to England began.

After Dorothy passes, Laurel and Gerry agree to become her final secret keepers, believing it will do little good now to recast their mother’s life to those who knew her. The pictures Laurel finds in the locket emphasize the new connection—the children Dorothy had with Stephen Nicolson overlaying the pictures of Vivien with her brothers and sister—her old family connected with her new, both held close to her heart in this precious item. Jimmy’s self-portrait likewise confirms Laurel’s connection with the secret, as she serves as the link between Jimmy and her mother. Dolly Smitham is foiled by her grand dreams, but both Vivien and Jimmy go on to enjoy long, happy lives beyond the shadow of war. Laurel’s carefree innocence in the final chapter closes the novel on a note of optimism and joy, and a suggestion that not all secrets are destructive—an addendum to the novel’s discussion of The Isolation of Secrets.