Within (2005)

Brad, Christina, T.K. and Kelly are on a post-graduation trip to Europe. Unfortunately, what starts out as a dream quickly spirals into a nightmare. Upon entering a 14th century castle, the friends find themselves trapped in a horrifying alternate realm where violent hallucinations overtake them. A stranger emerges, shocking them with the reality of their terrifying fate; one must stay behind - alone forever within the torturous stone walls, in order for the rest of the group to escape. As time runs out, hope and reason disappear, anarchy takes over and extreme violence erupts. Will it be male strength or female guile that will ultimately determine who will bear the terrible fate?

Mystery, Horror