Apt on AllMovie

A lonely department store employee uncovers a dark secret after moving into a new apartment in Phone director Ahn Byung-ki's low-key shocker. The Christmas rush is coming, and store designer Se-jin (Go So-yeong) is under pressure to assure that the store will be able to accommodate the formidable holiday traffic. Soon after moving into a new apartment building, Se-jin is troubled to note that the windows in the building opposite her mysteriously start to flicker every night at 9:56pm. One night, after being frightened by a mysterious woman in red (Yu Min) and watching a man plunge to his death at the precise time the lights go haywire, Se-jin strikes up a friendship with wheelchair-bound Yu-yeon (Jang Heui-jin), who lives alone next door. When a teenage acquaintance of Yu-yeon takes a deadly fall down an elevator shaft, the only person willing to believe Se-jin's incredible tales is a kindly policeman (Gang Seong-jin) who may hold the key to unlocking the mysterious building's deadly secret.