Married My Sister's Groom and Make Him Regret

Blanche Neville, mother of twins Hannah and Emma, offers Hannah one hundred million to pose as Emma for three years. The Neville-Percy partnership depends on the marriage, and Emma is gone. Hannah accepts because her dying grandmother needs the money. Hunter Percy, the Percy heir, is obsessed with his first love, Lisha Spears.

For three years Hannah lives as Emma. Hunter keeps her at a distance: the staff cannot call her ma'am, and his bedroom stays closed to her. When Lisha moves overseas, Hunter softens, promising to try to forget Lisha. Lisha returns, and that promise disappears.

In the last seven days, Hunter leaves Hannah alone on her birthday to see Lisha. Later he orders her to bring Lisha pads in the rain within thirty minutes. Lisha accuses Hannah of dumping ice on her. Hunter demands an apology and threatens the Neville-Percy partnership. Hannah kneels and apologizes to protect her grandmother's treatment. Hunter still punishes her with twenty buckets of ice.

After the ice punishment, Hunter takes Lisha to Paris. While Hannah is in the hospital, William Fitzroy, a billionaire's son, arrives on the first flight. He has looked after Hannah's grandmother in the countryside for five years. He plans to reveal his true identity and feelings to Hannah in three days. Hunter's mother then arrives and blames Hannah for Hunter's absence. She gives Hannah a choice: call Hunter back or take his punishment. Hannah takes the beating because if the deal falls apart, her grandmother loses treatment. Hunter returns, finds Hannah injured, and promises to come home earlier. Lisha pulls him back.

Lisha falls downstairs and blames Hannah. Hunter locks Hannah in the basement, knowing she has claustrophobia and asthma. Five hours later, Hunter finds her burning up with fever and calls a doctor. On the final day, Blanche confirms Emma is back and it is time to swap. Hannah receives the one hundred million and prepares to leave quietly.

Hannah gives Emma instructions about Hunter's habits and declares herself done with both families. At their anniversary, Hunter is with Lisha but chooses to go home to Emma. Hannah asks for one anniversary wish: “a lifetime apart.” She leaves. Emma returns, takes over, and tells Hannah to get out of Philadelphia. In the car, Hannah silently says goodbye to Hunter as she leaves Philadelphia. Emma and her mother notice the man picking her up looks like the heir of the Fitzroy family, and the Fitzroy family is way over in New York.