Fear Island (2009)

After a blowout party at a secluded island cabin, five friends make a shocking discovery: a dead body and the only boat off the island gone. Trapped and unable to call for help, they become prey to a mysterious killer seeking revenge. Together, they must decipher the murderer's chilling series of clues to reveal the island's secret past ... or face death one by one.

The police find an amnesic young woman alone in an island with a large knife covered in blood and her six friends have been murdered. Detective Armory suspects that she killed her friends but the psychiatrist Dr. Jamie Chalice tells him that she is in shock and need to be treated. Soon she recalls her name, Jenna, and Detective Armory calls her parents who are in Cambodia. While they are traveling back home, Jenna recites what had happened to the group of friends. The skeptic Detective Armory starts to feel sorry for Jenna, but Dr. Chalice feels that her story has many inconsistencies and something might be wrong