In Scott O'Dell's novel Sing Down the Moon, the most vital lesson the Navajo protagonist Bright Morning learns is the importance of loyalty.
Bright Morning gets her first taste of the importance of loyalty in the very beginning of the book. Early on, Bright Morning is tasked with the duty of taking her mother's large flock of sheep to graze at the start of spring. It's the first time she has taken on the responsibility herself and herds the sheep to a mesa at a spring in Canyon de Chelly. However, both she and the sheep are overtaken by a sudden late season blizzard. She manages to herd the sheep into a small canyon near the fork of the river, hidden by the big canyon, but she is so terrified that she winds up abandoning them. Because of the sheep's secure location, they survive the storm, but she can't shake the feeling of guilt since, due to the flock's size, the flock is very valuable to her family. She feels she has been disloyal to her family.
Bright Morning continues to learn the lesson of loyalty all throughout the novel. Another lesson happens with respect to Tall Boy, the man who becomes her husband. Tall Boy's arm is crippled from being shot by Spaniards who have enslaved Bright Morning and her friend Running Bird, but Tall Boy does not permit his crippled state from preventing him to fight with his warriors when his tribe is later attacked by Americans wanting to drive the tribe off the land. Even Bright Morning's father is surprised by Tall Boy's dedication and begs him not to fight, warning, "If you stay and cannot fight, what will happen? ... You will be killed. Others will be killed" (p. 75). Though the tribe is driven off the land and members slowly start dying, Bright Morning, out of loyalty to her family, returns to the canyon to raise Tall Boy's son in the security of the canyon on her own.