After the mysterious death of her undercover cop husband, a female martial artist must protect her daughter from corrupt police, politicians and hired assassins who will do anything to conceal the truth.

Rayya, who has inborn heart disease, befriends since childhood with Nico. For Rayya, the most important person beside her mother is Nico. And Nico is keeping Rayya carefully. Nico also knows all Rayya’s secrets, including the guys who had attracted her. Anyone can see that both of them have a sense of more than just friend. However, both keep that feeling to themself. One day, Rayya surprises because the guys from his past comes together without telling her. The love letters she wrote and kept in Whisper, a pretty box engraved with heart, was sent to the boys. They are Mike, Cello, and Addin. Rayya has not lost curiosity about who sent her love letters, when Nico suddenly disappears. Rayya becomes frantic.