Lee Jiyeon's Christmas pilgrimage home is a ritual of quiet solitude, a chance to outrun the echoes of a past she thought she had left behind. But a twist of fate—and a sold-out train—forces her into the one place she never expected to be: face-to-face with the boy who stole her heart and broke it, Park Minjun.

Trapped together on a long, slow-moving train in a blizzard, they are forced to confront the ten years of silence that have stretched between them. What started as an awkward reunion quickly melts into a slow-burn journey of forgiveness, shared memories, and a fragile, new hope. But with the train hurtling toward their shared past, will the man who once ran away finally stay? And can a love that was lost on a train find its way back home for Christmas?