Forbidden Siren (2006)

In 1976, on the southern island of Yamijima, the sea turns red, a siren begins wailing -- and all but one of the inhabitants disappear. The sole survivor is discovered with his mind gone and his eyes bulging with terror. Twenty-nine years later, Shinichi, a mild-mannered freelance writer, comes to live on the island with his grown daughter, Yuki, and his young son, Hideo. Shinichi hopes that the change of scenery will heal his sickly son. They are greeted on their arrival by the kindly Dr. Minamida, but the other inhabitants stare at them blankly, sullenly. Their house, deep in the forest, has not been inhabited in years -- and looks it. A neighbor lady comes calling and offers Yuki advice with a frazzled urgency: Don't walk alone at night, don't go to the steel tower on the hill -- and if the siren on the tower sounds, don't go outside. Yuki learns that her new home has other . . . peculiarities, including a sinister folk religion, strange graffiti, and an eerie folk song. Meanwhile, Hideo keeps wandering off. Then one day the siren starts wailing . . . and Yuki finds out what all the warnings really mean.