Hye-jeong, a lonely young girl who has drifted away from her family and avoids personal relationships, works in a factory, lives in a shared apartment, and leads an insipid and meaningless existence until one night she discovers that she has become a ghost.

A young woman in her 20s, Chae Meehee, visits middle-aged Cho Sungsook and insists that they were once childhood best friends. Though Cho Sungsook has never seen Chae Meehee before, they become closer at Meehee’s insistence. Their pasts cross paths as though they were traveling through time.