Who killed Ryan McKay's cousin? In suburban Westchester County, just outside the frenetic pace of New York City, a deadly murder occurs. After a violent struggle, FBI agent Shane Walsh is dead and his wife, Caitlin, has vanished. At the urging of a mysterious text, the Walshes' nine-year-old daughter, Kennedy, has been safely whisked away by a close family member. The FBI is determined to bring down whoever assassinated one of its own and is focusing on Caitlin as a prime suspect. Ryan McKay, Forensic Instincts' chief technology officer, as well as Shane's cousin and lifelong friend, vehemently disagrees. Ryan knows the Walsh family well. He insists that Caitlin is innocent, and that she, herself, is in danger. After convincing his team to cast a wider net, Ryan leads FI on a zigzag course across two continents to locate Caitlin, sidestepping the FBI at every turn, and protecting Kennedy at all costs. But the FBI is on the warpath, and threatens to permanently shut down Forensic Instincts if they don't back off. Undeterred by the FBI's threats, FI goes underground in pursuit of their rogue mission. As the pace quickens, Kennedy becomes the target of unnerving text messages. Both The FBI and the Forensic Instincts teams sense that the end game is near and that the chess match is spiraling to a stunning conclusion. Determined to declare "checkmate" before the killer, Forensic Instincts must not only protect Kennedy but make sure that their team doesn't end up as collateral damage when the king falls.