The Mark of Cain

Industrialist Richard Howard arrives in Bordeaux on a cotton-purchase mission and is immediately drawn to Sarah Bonheur. He spends much of his visit sightseeing, and the growing attraction complicates his business purpose. What starts as a professional encounter quickly becomes a personal infatuation.

John Howard arrives to close the deal and is swept up in a whirlwind courtship with Sarah. He marries her, bringing a new alliance into Richard's life and intensifying the love triangle. Richard's feelings shift from professional interest to romantic rivalry.

The couple moves to Manchester, where Sarah feels increasingly isolated. John spends little time at home and relies on a strict nurse, while a French nurse Sarah had engaged is dismissed. The household atmosphere grows cold as Sarah's unhappiness deepens.

Richard privately suggests to Sarah that John is having an affair and should be divorced, but he masks his encouragement as concern. He manipulates conversations to seed doubt within the marriage. The plan is not to fix things but to control Sarah's future.

A lawyer informs Sarah that she has no claim to the fortune she brought into the marriage due to the lack of a pre-nuptial agreement. She resolves to leave, but John strikes her and warns that she cannot take the child without his permission. This confrontation crystallizes the peril she faces if she tries to depart.

That night, John asks for forgiveness and vows not to oppose her departure with the child. He claims to love her and regrets his mistreatment, and Sarah admits she still loves him. The couple reconciles, though their fragile peace is soon threatened by growing suspicion and deceit.

John becomes dangerously ill, and Dr. White suspects poisoning but cannot confirm the cause. Richard continues to maneuver behind the scenes, slowly poisoning John while fanning distrust toward Sarah among the servants and the doctor. The true danger remains hidden as the illness worsens.

John dies after Richard ensures the circumstances point toward Sarah. Richard privately vows to ruin her by making him look innocent, even as he plots to shield his own involvement. He uses the doctor and servants to cast doubt on Sarah and to accuse her of murder.

Following John's death, Sarah is arrested and the prosecutor highlights her purchase of arsenic as incriminating. Richard has planted small traces of arsenic in Sarah's belongings, and insinuations of an affair with Jerome intensify the suspicion. The case looks dire as the evidence seems to stack against her.

Richard takes the stand and uses sharp, persuasive rhetoric to undermine earlier witnesses. His testimony sways the crowd and casts doubt on the prosecution's initial interpretation of the evidence. A crucial mistake later makes Sarah appear guilty, and the jury begins to doubt her innocence.

Realizing he may have failed to save her, Richard cries out that she is innocent in a desperate bid to salvage something. He offers no further help, admitting at least his power over the verdict has limits. Jerome, who believes in Sarah's innocence, resolves to uncover the truth behind John's death.

Jerome, deeply in love with Sarah and convinced of her innocence, resolves to uncover Richard's motive and the true events surrounding John's death. He begins a determined search for evidence to exonerate Sarah and expose the manipulation at the heart of the case. The film closes with the promise of a quest for truth that could overturn the verdict.