Kill Theory is a 2009 horror-thriller film directed by Chris Moore in his directorial debut and written by Kelly C. Palmer.
Plot
An unnamed man is sitting in a psychiatrist's office, being released from an insane asylum. His doctor, Dr. Karl Truftin (Don McManus), recaps how the man sacrificed his three friends during a mountain climbing expedition, cutting their climbing ropes in order to save himself. Although the man insists that anyone in his situation would have made the decision to kill to survive, the doctor explains that due to good behaviour and evident remorse over causing the deaths, the man is to be set free with regular psychiatric evaluation.
Meanwhile, Brent (Teddy Dunn) is travelling to his father's lakehouse with his girlfriend Amber (Ryanne Duzich), other couples Michael (Patrick Flueger) and Jennifer (Agnes Bruckner), Carlos (Theo Rossi) and Nicole (Steffi Wickens), as well as their friend Freddy (Daniel Franzese). Upon arriving they are surprised to find Brent's step-sister Alex (Taryn Manning) has been living there. Brent and Alex argue, however the others convince Brent to let her stay. After settling in, Amber refers to an unspecified event that implies she and Michael were intimate at one point, however Michael brushes off the topic quickly. The group party and drink into the night until everyone goes to bed. Carlos and Nicole decide to sleep outside on the porch. Carlos, being heavily intoxicated, passes out immediately. When Nicole goes into the kitchen to get a drink, she is attacked by an unknown man.
Sometime later, Nicole's body is thrown through a window onto Freddy who alerts the others with his screams. The group panic before noticing the word 'TV' cut into Nicole's stomach. After turning on the TV, the group view a video of Nicole being handed a loaded gun and told to shoot Carlos in order to survive. Nicole refuses and instead turns the gun on her attacker who overpowers her and slits her throat. The unseen man then explains to the group through a walkie-talkie that come 6 a.m. only one member of the group should be alive or they will all die. The man also explains that Nicole was given the same option as they are, kill to survive, however she failed. Collectively the group decide to barricade themselves into the house, realizing their phones do not work. Carlos decides to make a run toward the boat to retrieve a gun placed in the key box. Brent follows him and they find the boat has been sunk, but Brent is able to retrieve the gun anyway. Noticing a nearby axe, Carlos runs to get it, but is caught in a giant bear trap. Brent begins to help him, however after hearing someone approach from the trees nearby he leaves Carlos and returns to the house, telling the others that Carlos has been killed.
While Freddy begins to become hysterical over their situation, a bandaged up Carlos makes it to the house. Although barely conscious, Carlos is able to tell Jennifer that Brent had left him. Jennifer manages to knock the gun out of Brent's hand and gives it to Michael, no longer trusting Brent. The group decide they have to try and leave in the van in order to get Carlos to a hospital despite Brent's protests and expectation that the van will be rigged to explode. Alex leaves the house and successfully brings the van to the front door of the house, allowing everyone to get in. However, while driving away from the house, road spikes blow all of the tires. The unnamed man quickly shoots rigged balloons of gasoline which spill over the van before telling the group that there is no escape and that they need to sacrifice one person in the next 60 seconds or they will all be burned alive. Brent pushes the wounded Carlos out of the van where he is shot in the head.