Seventeen-year-old Andrew begins a journal after receiving it as a gift from his older brother, Julian. During a family hiking trip, Julian ventures into a mysterious cave and comes back visibly disturbed. Shortly after, he disappears without a trace, leaving his family devastated.
Ten years later, Andrew and his brother, Jack, return to the same cave, determined to uncover the truth about Julian’s disappearance. As they explore, they encounter strange symbols, unsettling whispers, and an ancient lagoon hidden deep within. The deeper they go, the more they realize that they may have uncovered something far more terrifying than they ever imagined.