Set in 1850, The Winter Promise follows Opal Sharp and her younger siblings who become orphaned and destitute. The story takes a darker turn when illness strikes, and their brother Charlie, desperate to save his siblings, makes a heartbreaking decision: he takes the younger children to the workhouse. When Opal discovers what happened, she is devastated.
 
Alone and homeless, Opal eventually becomes a lady’s maid for a woman named Mrs King. While working in this new household, she begins to feel a sense of security — but things are complicated when her mistress’s son begins showing her attention. Meanwhile, Opal’s greatest wish is to be reunited with her siblings. The novel centers on her promise to bring her family back together and whether she can fulfill that vow despite the many obstacles in her path.