Two American girls, Emily and Sophia, embark on a vacation to Montenegro to visit an old friend. While exploring the island, they stumble upon a mysterious fortress called Mamula, which is located on a remote island. As they venture deeper into the fortress, they discover that they are not alone. There, they encounter a mysterious man named Alexei. He claims to be a local guide who has been living on the island for years. However, his past is shrouded in mystery, and he seems to have a deep connection to the island's dark secrets. As they explore further, they uncover more evidence of a sinister plot involving the fortress and its inhabitants. They realize that someone else is on the island with them, and he will stop at nothing to protect its secrets. The island is filled with darkness and shadows, and the terror has just begun. The girls soon realize that their old friend was not who they thought he was, and that he had been involved in some nefarious activity. With their lives in danger, the girls must use all their wits to outsmart their mysterious companion and uncover the truth behind the island's dark history. Can they escape before it's too late?