In the early 20th century, in the wilds of Montana, Colonel William Ludlow retires from military life to raise his three sons in the remote foothills of the Rocky Mountains. The Ludlow boys - Alfred, the eldest, disciplined and dutiful; Tristan, the middle son, wild and fiercely independent; and Samuel, the youngest, idealistic and naive - grow up close, bound by the rigors of frontier life and the love of their father. Their bond is tested when Samuel brings home his fiancée, Susannah, whose beauty and grace captivate all three brothers, planting the seeds of jealousy and setting into motion rivalries that will shake the foundations of their family.

The outbreak of World War I forever alters the lives of the Ludlow family. Despite their father's objection to the war, all three brothers enlist to fight abroad, seeking glory and honor. The horrors of war mark them in profound ways, driving wedges between them and changing their paths forever. As they return to the changing world of their Montana home, each brother struggles to find their place in a post-war America, contend with their feelings for Susannah, and reconcile their personal dreams with the stark realities that face them.