Immortal in Death by Nora Roberts

The source material details a complex police investigation led by Lieutenant Eve Dallas, focused initially on the murder of a man named Boomer and subsequently the murder of high-profile model Pandora, for which Dallas's friend, Mavis Freestone, becomes the prime suspect. As Dallas and her partner, Peabody, pursue leads, they uncover connections between the victims and a potent, illegal new drug called "Immortality," which is highly addictive and ultimately lethal. The investigation involves interviewing multiple suspects—including Pandora's designer Leonardo, his friends Justin Young and Jerry Fitzgerald, and producer Paul Redford—all while Dallas grapples with procedural pressures, her personal life with Roarke, and traumatic memories from her past. The narrative culminates in the discovery that an undercover cop, Lieutenant Casto, was the actual killer, driven by greed for the drug's profits and a need to cover his tracks, securing Mavis's freedom right before Dallas's wedding.