Devil in the Lake.

Bo Young moves into the mansion of the previously wealthy grandmother, Wang, as a caregiver with a dangerous intention. Mother Kim, the only blood relative of Wang who hired Bo Young, sets conditions such as 'Do not bring anyone, especially children,' and 'Do not go near the reservoir'. Ominous and bizarre signs continue in grandmother Wang's huge mansion located next to a reservoir called 'Gwimot', where people are dying, and Bo Young finds out that foreigners who have visited the place have suffered a mysterious death...