In New York, a city of glitz and sin, the multinational biotech giant "New Era" is advancing a forbidden project called "Prometheus," aimed at reshaping world order through genetic weapons. Young Sarah, due to her rare genetic makeup, becomes the project's core "living key," her life hanging by a thread. To protect her only family, her sister Lexi—on the surface a gifted sculpture student at an Ivy League university, but in reality the infamous top‑tier assassin "A" on the dark web—is forced to deal with the devil, becoming New Era's blood‑stained blade for eliminating obstacles. Until one rainy night, she crosses paths with Hunter, an elite FBI agent with a hound‑like sense of smell and an almost obsessive intuition. He catches the lingering scent of gunpowder and blood on her, and a deadly dance begins—one that starts with instinctive pursuit, gets tangled in schemes and conspiracies, and ends in life‑and‑death devotion.