Elite assassin Stella signs a three-month contract with mafia heir Damon, posing as his wife to serve as his human shield in exchange for ten million dollars. Hiding her nyctophobia and secret past, she repeatedly pulls off desperate counterattacks amid family infighting, exposing his uncle Victor's power-grabbing conspiracy and the truth behind an old massacre. From mutual suspicion to sharing life and death, Damon tears up the contract and begs her to stay. In the end, Stella wears the matriarch ring, evolving from a disposable shield into the true mistress of the family.