In the booming frontier city of Denver, 1873, U.S. Marshal Sam Slick finds himself on high alert as the arrival of the railroad has transformed the town, swelling its population to 25,000 and bringing an influx of newcomers, opportunity, and peril. Amid this surge of strangers, a darkness stirs in Denver's streets. Amid the bustling chaos, a new terror grips the city-a twisted serial killer who calls himself the Rocky Mountain Reaper. Cold and calculating, the Reaper targets not only innocent women but seems fixated on Sam and his family, leaving gruesome clues and cryptic warnings. Driven by a relentless thirst for blood, the killer is unlike any threat Sam has faced, preying on the city's darkest corners and leaving fear in his wake. Sam knows he must stop this predator at all costs, as the Reaper's thirst for revenge threatens to spill over into his own family's lives. He embarks on a deadly hunt, navigating Denver's chaotic growth, outsmarting foes, and protecting the city from dangers that extend beyond his world. With his family and his city hanging in the balance, Sam must unravel the Reaper's twisted mind and face dangers from both this world and beyond-proving, once again, that he is the right man to stand guard on the edge of history.