The Outsider is a story of forbidden love and redemption framed within the western genre. It revolves around Rebecca Yoder, a young widow and member of an Amish community of "Plain People", and Johnny Gault, a gunslinger who collapses on her propoerty severely wounded. Because Rebecca's religious beliefs do not allow her to turn away anyone in need, she takes the stranger into her home. She sends for the doctor, but because of Johnny's serious condition, he advises Rebecca that Johnny should not be moved from her home.
She nurses the gunman back to health, and during that time finds herself attracted to him. Her son, Benjo, forms a strong attachment to him as well. The Amish community objects to an "outsider" staying with her, particularly Noah Weaver, an old friend and potential suitor.
After much soul searching, Rebecca and Johnny make love, only to be caught by one of her neighbors. Outraged by Rebecca's actions, her father and the rest of the community insist that she end the relationship and repent. At first she acquiesces, but during her confession to the community, she begins to question whether or not she can end the relationship because she truly loves him and she does not believe that God would want or expect her to give him up.