In the late 19th century, Col. John Henry Patterson, a British engineer, is tasked with overseeing the construction of a railway bridge over the Tsavo River in East Africa. When he arrives, the project faces unexpected dangers: a pair of maneless male lions begin terrorizing the workers, disappearing into the night as mysteriously as they appear. Known as "The Ghost" and "The Darkness," these lions kill with a seeming malice and create an atmosphere of fear and chaos among the workforce. Patterson, who initially believed the tales of vicious lions to be exaggerated, quickly realizes the severity of the situation after several attacks leave workers dead and morale shattered. As the body count rises, the pressure on Patterson to either halt the bloodshed or complete the bridge mounts, and his professional reputation is on the line.

To counter this threat, Patterson enlists the help of esteemed professional hunter Charles Remington, who brings his expertise and unique approach to tackling what he deems to be more than just rogue animals. The two forge an uneasy alliance, tracking the cunning predators through challenging terrains, applying both ingenuity and sheer nerve in their strategies to stop the lions. With mounting political pressure back in England and tensions high among a terrified workforce ready to abandon the project at any moment, Patterson and Remington's mission becomes not just a battle for survival but a deeply personal struggle against fear itself.