Into the M|rror (2003)

Former policeman Woo Young-Min (Yoo Ji-Tae) is emotionally crippled by the memory of a botched hostage situation that resulted in the end of his career and the death of his partner. Withdrawn and filled with self-loathing, he now works as a security guard in a department store that is set to reopen after a fire.

After a spate of gruesome and suspicious suicides in the store, Young-Min is obliged to investigate out of a sense of duty to his uncle, the store’s chairman. While the police, led by a resentful former colleague, begin to suspect the work of a serial killer, Young-Min investigates a less logical route of enquiry after apprehending a trespasser who believes her twin sister is responsible, despite having perished in the store blaze.