One winter night in 2015, an unidentified pregnant woman with no belongings is rushed into the hospital where Imaizumi Nao works. This pregnant woman shows signs of an attempted suicide which disturbs the hospital's workers. Nao devotes herself to the nursing of this mysterious pregnant woman that does not speak at all. Mie, a nurse and the only daughter of the current director, sometimes sees the mysterious woman wearning an ominous smile...