Spoilers ahead for Jean Hanff Korelitz's "You Should Have Known." The HBO drama "The Undoing" (opens in new tab), starring Nicole Kidman and Hugh Grant, is loosely based on Jean Hanff Korelitz's 2014 book "You Should Have Known." But the title is not the only difference between the book and the series. Because it is a loose adaptation, there are many details and plot points that did not make it into the series. The ending of the series has not yet been aired, but since the story has already taken a different path, the ending of the book will most likely be quite different from the series.

Nevertheless, for those who are wondering how "You Should Have Known" will end, let me describe the book and its ending. (No spoilers for the TV show.)

One major difference from the series: Jonathan only appears in the past tense in the novel. He is already gone when the book begins, and he is on the run until the last page. He is also unquestionably guilty. Throughout the novel, he confesses to the murder in a letter to Grace, trying to manipulate her into abandoning her new life.

In the book, there is no trial. Nor is there a capture at the beach house. (There is a beach house, but Grace and Henry remain there throughout the novel, and Jonathan never appears.) Jonathan's ghost haunts the novel, but he never appears in the contemporary scenes. At the very end of the book, Jonathan is captured by Interpol and extradited back to the United States. The book's story is simpler, and the ending more bittersweet: yes, Jonathan killed Elena (known as Malaga in the book).

Remember That Beach House" Now, in the novel, Grace and Henry never leave the beach house. Henry starts school nearby, Grace reunites with an old friend (her former best friend, in fact, a woman who recognized Jonathan as a sociopath), Grace and Henry rescue a dog, winterize the beach house, Grace's father comes to visit, and they repair their relationship. All of this happens while Jonathan is on the run.

One of the reasons Grace and Henry were able to adjust so well to their new lives is because Henry thrived there. He loves his new school (much more than Rearden liked it), makes friends quickly, and seems to have recovered from the loss of his father. While he is at school during the day, Grace takes time to grieve her marriage and the life she has left behind, process everything that has happened, and adjust to the reality of her new existence.

The friend Grace reunites with is expanding her own mental health practice nearby, and Grace decides to close her New York practice and work with her old friend. There is even a kind of happy ending: by the end of the novel, Grace has moved on and kissed a local man who has become her best friend. He is the opposite of Jonathan, lacking in charm, but kind and decent, and seems to be just what Grace needs.

In an interview with Marie Claire after the finale aired (open in new tab), director Susanne Bier said: "The series uses the book [as inspiration] in the first two episodes, but as a kind of conceptual framework . The idea of 'regulating the truth' and 'processing the truth the way you want it' is a very important issue, and we all felt that we were doing a really fun, really funny hodgepodge of hodgepodge, but at the heart of it was the philosophy of that (book)."