A song like a miracle falls in front of 20-year-old Joseph who has nothing. One day while they were having a happy time singing 'that song' like fate, a man with everything, even the owner of the song, appears in front of Joseph.
Thud! Thud! Thud! The noise between rooms 401 and 501 has started! Eun Soo, an aspiring writer who is no different from a jobless person, begins to observe the owner of the house upstairs, questioning the noise between the floors that tormented her while searching for a subject for a contest. Ho Kyung, the man upstairs, also began to notice the existence of Eun Soo and eventually, Eun Soo faces a shocking truth... The noise that started today "Is the story that I only imagined real?’"