In 1872, Indian fighter Johnny Mackay goes to Washington to discuss with President Ulysses S. Grant the violence along the California-Oregon border caused by a renegade Modoc Indian chief, Captain Jack. Grant appoints Johnny Peace Commissioner and asks him to convince Captain Jack, whom he has known a long time, to return to the reservation. Johnny escorts Nancy Meek, the niece of a retired army colonel, back west. On the stagecoach journey between Sacramento and Oregon, they are attacked by Indians led by Modoc Jim, one of Captain Jack's men. After stage driver Bill Satterwhite's sweetheart, Lily White, is killed, Bill swears vengeance on all Modocs. When Johnny drives Nancy to her uncle's ranch, they discover that it has been raided and burned, and her aunt and uncle killed. At Fort Klamath, Toby and Manok, the daughter and son of the old Modoc chief, tell Johnny that most of the Modoc want peace but are unable to control Captain Jack. After Toby proposes that Johnny kill Captain Jack, he replies that he intends to talk peace. When Toby, who is in love with Johnny, suggests that if she becomes his wife, no Modoc will ever harm him, Johnny gently turns down her offer. At Lost River, Captain Jack's territory, Johnny reminds Captain Jack that he signed a treaty agreeing to live on the reservation. However, Captain Jack, wants to take over all of Lost River and drive out the settlers. As Johnny leaves, Bill rides up and starts shooting, killing Modoc Jim and causing the other Indians to go on a killing rampage. The Modoc take refuge at a mountain stronghold, and when the Army, led by General Gilliam, attempts to storm the stronghold, they are defeated and have to retreat to the fort. Later, General Canby is instructed by the Secretary of War to cease all operations against the Modoc and make another attempt to achieve peace, but a peace with honor. Manok and Toby arrange a meeting between Captain Jack, Johnny, Canby and other interested parties, and both sides agree to come unarmed. Johnny, who has fallen in love with Nancy, asks her to promise that she will leave if the peace talks fail. At the meeting, Captain Jack reiterates his demand that all the settlers leave the Lost River area, then suddenly draws a gun and starts shooting at the peace party. Toby is killed while trying to protect Johnny, who is wounded in the attack. President Grant then authorizes Johnny to track down the renegades. As Johnny rides out with the soldiers, Captain Jack and two of his braves, Scarface Charlie and Bogus Charlie, split up, and Johnny pursues Captain Jack while Bill and Manok go after the others. Manok catches and kills Bogus Charlie, but Scarface Charlie suprises Bill by telling him that they will surrender. After initially being pinned down by Captain Jack's rifle fire, Johnny overpowers him in a rapidly flowing stream and takes him back to the fort as a prisoner of war. After Captain Jack's trial, as preparations are made for his hanging, Johnny visits him in his cell where they discuss meeting one day in their respective heavens and part as friends. After peace finally comes to the area, Johnny and Nancy plan a life together.