Hide and Seek (2013 film)

Hide and Seek Hangul RRSumbakkokjil is a 2013 South Korean mystery film written and directed by Huh Jung in his feature directorial debut. It revolves around two families who believe strangers to be living in hiding in their homes, and struggle to fight back.

One day, Sungsoo receives a phone call that his brother is missing and goes to his brothers apartment building for the first time in decades to look for him. There, he finds strange symbols carved into every door and meets Joohee and her young daughter. Joohee is convinced that someone is spying on them and lives in constant fear.Sungsoo figures out that the symbols carved onto the doors are hide and seek codes that indicate gender and number of people. Then when he returns home, he finds similar symbols carved into his door. ........

Source: Wikipedia