In a Korean boarding school, a legendary staircase with 28 steps is said to grant a wish to the climber when the 29th step appears. A lesbian ballet student, Kim So-hee, is deeply in love with her girlfriend, Yoon Jin-sung, but Jin-sung finds the mysterious step and makes a wish to surpass So-hee in a Russian ballet school competition. However, the wish comes with an unknown price, resulting in So-hee's accidental death. Meanwhile, a bullied student, Eon Hae-ju, finds the step and wishes for So-hee's return, leading to tragic consequences.