Ruby Weaver's curly red hair isn't the only thing that sets her apart from her Amish community in 1863. Twenty-eight and single, Ruby doesn't believe a woman needs to be married in order to be happy. Her ailing friend Lovinia Fischer, however, has other ideas and wants Ruby to promise to marry her husband after she dies. Never imagining she'd have to fulfill that vow, Ruby agrees. And she's not the only one. Lovinia has extracted a similar promise from her husband, Gideon.

With both Ruby and Gideon reluctant to keep their promises, a compromise must be reached. Ruby will spend her days with Gideon's family—helping to raise the children and keep the house—but her nights will be spent at her sister's neighboring house. But this arrangement raises eyebrows in their conservative Amish community, and it soon becomes clear that Ruby must make a decision—marry Gideon or turn her back on her friend, the children she's grown to love . . . and their father.