In the climax of the movie, Edith Cushing (Mia Wasikowska) discovers the dark secrets of Allerdale Hall, also known as Crimson Peak, the mansion where she now lives with her husband, Sir Thomas Sharpe (Tom Hiddleston), and his sister, Lucille Sharpe (Jessica Chastain).
Edith learns that the Sharpe siblings have a history of murdering wealthy wives to inherit their fortunes. Sir Thomas, whom Edith had married, was no exception. Lucille is revealed to be the mastermind behind these murders, driven by her possessive love for her brother and her desire for wealth.
In the resolution, Edith, who narrowly escapes being poisoned by Lucille, confronts Lucille in a final showdown. A violent confrontation ensues, and Edith is ultimately able to overpower Lucille with the help of a spectral ally, the ghost of Thomas’s first wife, Lady Beatrice Sharpe.
Edith and Sir Thomas share a poignant moment before he succumbs to his injuries, and Lucille meets her demise as well. The siblings die together in the snow-covered garden of Allerdale Hall.
The film concludes with Edith returning to America and writing a novel about her experiences. The final scenes suggest that Edith has moved on with her life, though she is haunted by the ghosts of the past. She becomes a successful author but continues to be connected with the supernatural.
In summary, “Crimson Peak” ends with Edith surviving the dark secrets of Crimson Peak, overcoming the threat posed by Lucille, and finding a form of closure. The film combines elements of horror, romance, and mystery, with Guillermo del Toro’s signature visual style and Gothic storytelling.