Return of the repressed

"Freud coined the term "return of the repressed" to explain the existence of neurotic symptoms. He theorized that an unconscious thought/feeling (Id derived) would constantly press for access to the executive fictions of the mind in order to be discharged. The Ego would be on constant alert to prevent the direct expression of the forbidden idea but the idea would find a disguise and surface as a symptom." (source: http://shrinkwrapped.blogs.com/blog/2006/03/the_return_of_t.html)

In simpler terms the "return of the repressed" means a bad memory of experience being put to the back of someone's mind "reressing" the memory. The person will likely have no memory of this. This plays a large role in horror films as the horror genre often contains heavy themes of phycological behaviour. A repressed thought could be used as a plot device as a series of flashbacks or dream sequences could be used to have a character remember repressed memories, leading the audience to question the characters mental health. Having the mind make decisions that a character is no aware of is also important as the audience may also question what else the haracter could be doing without knowing, if that character in in an antagonist role. This idea could also be applied to the protagonist as i could imply tha what the "villain" has subjected them to in the past was so terrible that their mind had to block it out.