The top-ranked female assassin known as 'Snow Fox' perished during a mission and underwent a mysterious soul transformation into the body of Cassandra. Her new life begins with a fated one-night stand with Brandon, the city's most prominent billionaire. Five years later, Cassandra returns from abroad with her brilliant son, Bryson. When Bryson is taken by Brandon, Cassandra has no choice but to assume a secret identity as Brandon's personal bodyguard to stay close to her child. Through their daily life-and-death interactions, the assassin and the tycoon fall deeply in love, culminating in a perfect family reunion. The world's deadliest mother and its most powerful father are about to become the city's ultimate power couple. Success and heart follow.