Private investigators Harry Caine and Mona Morgan are gaining notoriety in south Florida as a smart, tenacious team who can solve cases no one else will touch. When a wealthy Palm Beach matron learns about their recent successes, she hires them to reinvestigate a 10-year-old cold case: The homicidal poisoning of her then 20 year old daughter. Harry and Mona go on the hunt. With help from a Federal Immigration officer and a retired FBI profiler, they unearth new evidence including the killer’s identity, his bizarre M.O., and a string of unsolved homicidal poisonings over the past decade that appear to be the work of their suspect. The hunt takes them to the Florida Keys and back, and a final confrontation in Miami’s Little Havana. During the investigation, Harry confronts a truth that could change his relationship with Mona, forever.