The Secret tells the story of Kaifeng (Played by Leon Lai) who loses his wife (Played By Wang Luodan) in an avalanche during an anniversary trip. Unable to move past his loss, his wife returns as a ghost to live with him.

Kaifeng wakes up with a terrible hangover. His heart aches for his lost wife, Qiujie, as memories of the accident rush back to him.It was meant to be a romantic climbing holiday. Both passionate climbers, they decided to summit a mountain in the Himalayas to celebrate their anniversary. But an avalanche dooms him to a lifetime of regret. Qiujie, the love of his life, mother of his son, is gone forever. In despair, Kaifeng turns to a spirit medium for advice on how to bring her back. And to his shock and joy, Qiujie really does come home. But she remembers almost nothing, including their son, and has no memory of the fatal accident. "Only those who love Qiujie will be able to see her spirit. You must never let her know that she's a spirit or she will disappear forever", says the medium. Kaifeng knows that she will not be able to stay forever. He can only try to keep the secret as long as possible with his son. Without letting her know, they try to keep her indoors and away from others while blissfully reliving the wonderful times they had before the accident. Soon the Himalayan climbing accident is uncovered and a body found. The police begin their investigation. At the same time, Qiujie discovers at a party the devastating truth that no one there can see her. She realizes that she is a spirit that must soon part with her husband and their son. She completely falls apart. Using the short time remaining to her, she works to leave a fitting legacy of memories for the future of her family.