A young brother and sister return to the island where they grew up, only to find it flooded, decayed, and scarred by war. Now overrun with grotesque, monstrous creatures, the ruined home holds their three missing friends somewhere within its horrors. Traveling by boat and on foot through drowned villages, a lonely lighthouse, and a dilapidated orphanage, the siblings must hide from and outwit the nightmarish things that hunt them as they search for their friends and confront the dark secrets of their shared past.