The central plot twist of "Gifted" is the revelation of the full story behind the suicide of Mary's mother, Diane. Through the course of the custody battle, it is revealed that Evelyn's relentless pressure for Diane to focus solely on mathematics, to the exclusion of a social life, led to her profound unhappiness. Frank discloses that Diane had solved the Navier-Stokes problem, a major mathematical challenge, but instructed him not to publish her work until after Evelyn's death. This posthumous act of defiance underscores the depth of Diane's resentment towards her mother and her desire for Mary to have a different, more fulfilling life.
The film's climax sees Frank making the heart-wrenching decision to place Mary in foster care to protect her from Evelyn. However, he soon discovers that Evelyn has violated their agreement by supervising Mary's education at the foster home. In a final confrontation, Frank presents Evelyn with Diane's completed work, using it as leverage to regain custody of Mary. The ending provides a compromise: Mary returns to live with Frank but also attends college-level courses to nurture her gift, allowing her to have both a loving home and the intellectual stimulation she needs. Evelyn, humbled and confronted with the consequences of her actions, is left to grapple with her daughter's final message.