Catherine, an airline ground staff member, secretly marries the president, William. She discovers she's pregnant and plans to confess, but William ignores her in public, giving flowers to his stepsister Sarah, who has just returned from abroad. Sarah had once saved his life, and Sarah bluntly tells Catherine that Sarah is just a substitute. Memories unfold: Sarah's mother, Ashley, was Catherine's father's mistress; the two stole the inheritance, and Catherine's mother, overwhelmed by the shock, was in a car accident and became a vegetable. Sarah then moves into their marital home. William privately admits that marrying Catherine is just a formality, and his heart belongs only to Sarah. Catherine endures her days in silence, her hopes met with constant neglect and humiliation. When Catherine's mother falls seriously ill and urgently needs imported special medicine, William prioritizes giving the medicine to Sarah's mother, causing Catherine's mother to miss her chance for treatment and die. At Catherine's mother's funeral, a tree collapses, and in a moment of crisis, William only protects Sarah, causing Catherine to fall and suffer a severe hemorrhage, resulting in a miscarriage. Heartbroken, Catherine secretly slips divorce papers into financial documents, tricking William into signing them to dissolve the marriage. Catherine's true identity is the top hacker ZERO. She joins Owen's tech company and marries Owen, who has secretly loved her for years. Subsequently, William's airline suffers a massive virus attack, crippling its entire system and causing devastating losses. While searching for the legendary hacker ZERO, they unexpectedly discover that ZERO is actually Catherine. At a charity gala, Sarah attempts to impersonate ZERO to gain resources, but Catherine exposes her. William investigates thoroughly and learns that it was Catherine, not Sarah, who saved him years ago, and Sarah's lies are exposed one by one. Knowing the truth, William kneels in repentance in the rain, only to be coldly rejected by Catherine. Driven mad with jealousy, Sarah hires thugs to frame Catherine and attempts to run her over with her car. Owen saves Catherine at the last moment, but suffers amnesia after treatment. Sarah then impersonates Owen's wife to sow discord between them. Owen's amnesia is only temporary; he quickly regains his memory and feigns cooperation with Sarah. At the company's anniversary celebration, Owen publicly exposes Sarah's hit-and-run crime. Desperate, Sarah recruits William, planning to set fire to Catherine and Owen's home. William, having already seen through the deception, warns the police beforehand, and Sarah is caught red-handed at the scene of the arson. Ultimately, Sarah is imprisoned, William is left alone, living in regret, while Catherine and Owen establish a critical illness charity fund named after their mother, welcoming a new life and living happily ever after.