Oregon Travail by Douglas Hirt
Kit Carson knows that trouble is brewing as he tracks a band of Blackfeet, but he isn't expecting to come upon the remains of a brutal massacre. The Blackfeet had butchered a small group of Shoshone, leaving behind nothing but maimed bodies--and one crying baby. Kit sets out to bring the baby back to his people but the Shoshone find him first--after they'd found the bodies of their people. They had only revenge on their minds. And with Kit holding the one small survivor of the massacre, he's their only suspect.