In a dark and Gothic world of the 19th century, the story follows Edward Markham, an artist who returns home after his stay in a mental institution where he received treatment for his madness. Edward has been tormented by memories of his brother, who fell victim to a violent tragedy and whose secret is a burden that Edward carries in his heart. Upon returning, he discovers that life at home is not as he left it. His wife, an intriguing and seductive woman, is involved in a web of darkness and desire, while a series of mysterious deaths begin to occur around him.
Desperate to uncover the truth and free himself from his own demons, Edward is pushed into a spiral of madness and revenge. With these elements at play, the story delves into dark territory, where the line between reality and madness blurs. As family secrets unravel and unsettling revelations emerge, the conflict between love, betrayal, and despair intensifies.
With a chilling atmosphere, the narrative unfolds unexpected twists that keep the viewer on the edge of their seat. In this game of shadows and revelations, what lies within the enigmatic coffin of the title becomes a powerful metaphor for the ghosts we all carry inside us, ready to come to light with each shocking revelation.