As the Runaway Train family gathers in Savannah, Georgia for the wedding of its last single member, Rhys McGowan, to Allison Slater, Jake's little sister, Rolling Stone magazine prepares an issue to celebrate the union. While focusing on the happy couple, they also sit down with Brayden and Lily Vanderburg for a feature on successful rock star marriages. After all, the two have been a couple since they were sixteen years old. But there is more to the story than meets the eye, and their love took a slight detour before finding happily ever after.
Told in flashbacks from the present to the past, Brayden and Lily share the story of their unbreakable love.