** CONTAINS SPOILERS
When HOLLY PARKER, a San Francisco shop girl, marries wealthy CLAYTON ANDERSON, it seems like a fairy tale, especially when he drives her up to the family mansion, complete with staff. Claytons domineering, possessive mother, ESTELLE, affects happiness for her son, but shes jealous and suspicious of Holly, suspecting that shell damage her ambitious sons rise in politics.
The first few years of the marriage pass with relative success, and they have a child, CLAY JR., and although there are moments of joy, Holly begins to resent the large amounts of time that her husband spends away on business. Subtly manipulated by Estelle, Holly keeps up her social obligations, soon drifting into an affair with PHIL BENTON. When she tries to break it off with Benton, he becomes violent, accidentally falling down his apartment stairs to his death. Panicking, Holly flees the scene, leaving behind evidence that she was there.
At home, Holly runs into Estelle, whose private detective knows of Hollys presence at the scene of Bentons death. Holly wants to tell the truth to Clay, whos out of town, but Estelle warns that it will destroy his career if Holly is accused of murder. Offering an alternative, Estelle demands that Holly fake her death in a boating accident and disappear to Europe, where a bank account will be set up for the rest of her life. Holly agrees reluctantly, says a tearful farewell to both husband and child, then goes ahead with the plan.
In Europe, Holly tries to start a new life with a pseudonym and new hair-do, but the pain of separation follows her everywhere, and she soon collapses in the snow, found by pianist CHRISTIAN, who takes her to his villa. Holly convalesces, and although a warm relationship grows between her and Christian, she knows she can never marry him. Indeed, she eventually leaves him, referring to herself as "dead."
Holly becomes an alcoholic, eventually landing in a cheap Mexican motel. There, she meets DAN SULLIVAN, a con man, who soon suspects the truth of her past. When he tries to manipulate her into a blackmail scheme against Clayton Anderson û now a New York gubernatorial candidate û a horrified Holly refuses. When Dan insists, Holly shoots him fatally.
Arrested for murder, Holly slips into catatonia, refusing to speak, booked under the name "Madame X." Her case is turned over to a young public defender, who she does not realize is her son, Clay Jr., grown up! Clay Jr. feels an unaccountable love for this mysterious woman, and he tries her case. Meanwhile, Clay Sr. and Estelle watch from the courtroom, gradually suspecting that Madame X might be Holly. Holly/Madame X, meanwhile, addicted to absinthe, is gravely ill, barely able to endure the arduous trial.
Holly soon finds out who Clay Jr. is, feels proud of what he has become, but doesnt divulge it to him, preferring to keep alive his memory of a fine, upstanding mother. She talks of a son she has abandoned, never telling Clay Jr. that hes the one. Meanwhile, Clay Sr. and Estelle also realize who Madame X is, but keep silent. Collapsing in court and carried to a back room, Holly tells Clay Jr. that she loves him just like a son, then dies in his arms. A devastated Clay Jr., uncertain why he feels such love for a virtual stranger, feels theres no use going on with the trial, but Clay Sr., knowing the truth but keeping Hollys secret, tells him its more important than hell ever know û indeed, without