The series, hosted by McFadden, recounts detectives' pursuits to solve a complicated murder investigation with a startling twist: the perpetrator is a fellow member of law enforcement.

Featuring interviews with those closely connected to the case and expert insight from McFadden, who has solved hundreds of homicide cases during his own career, each story reveals just how difficult and dangerous it is when the killer is on the inside. Staged and covered up crime scenes make the investigations all the more complex. But these dedicated detectives are committed to capturing the criminals and bringing them to justice, no matter the cost or badge they wear.