During the American Civil War, a Union officer is tasked with leading a small, fractured unit on a mission into Mexico. This group is made up of disparate forces, including Confederate prisoners of war, Union cavalrymen, and civilians. Their goal is to capture an Apache war chief who has been conducting raids into Texas. To succeed, the leader must navigate the complexities of managing a unit filled with tension and mistrust, especially between the Union soldiers and their reluctant Confederate allies. The journey into hostile territory forces the men to confront their personal prejudices and divides, while also dealing with the harsh landscape and the ever-present threat of a well-armed and elusive enemy.

As they venture further into Mexico, challenges mount both within the ranks and from outside forces. Supplies dwindle, morale fluctuates, and the threat from local guerrilla fighters and French troops in Mexico adds complexity to their mission. The dynamics within the group become increasingly strained, with differing perspectives on loyalty, justice, and leadership being challenged at every turn. The expedition becomes as much about survival and honor as it is about capturing their target. As the unit pushes deeper into danger, each member must decide where their true allegiance lies, testing the resilience of the few alliances that were forged along the way. The unfolding events force the characters to grapple with the costs of war and the burden of command under extreme uncertainty.