A disclaimer in the opening shot reads: "In February 2007, ten people went to the remote mountains of Northern California to shoot an adult movie. What happened next was something no one expected, but everyone saw coming."
On a snow-covered mountain, a bus, truck, and a few cars arrive at a remote camp area to film a porn film. The group makes up of professional porn actors Ron Jeremy and Veronica Hart (more or less playing themselves), novice porn stars Rock (John Edward Lee), Angel (Carmen Hart), Wanda (Jenny Guy), Lance (Bart Fletcher), as well as the director and producer Jim (Jeff Denton), cameraman T.J. (Caleb Mayo), gaffer-electrician and sound guy Jonah (Jason Graham), and makeup and script girl Laura (Amber Benson).
After being dropped off by the school bus driver who leaves them behind, the group settles in their living quarters for the next few days to shoot. While Laura talks with Ron about his past career days, the guys, Lance, Rock and T.J. talk about T.J.'s latest suck-and-squeeze device for carnal pleasure that Jim wants to market, while Angel and Wanda talk about their experiences on the porn sets. Radio reports begin to describe a "strange light" in the sky that has been hovering over the mountains for the last several hours as Jim gets down to directing, starting with the first scene with Ron and Veronica. During a break in filming, Jonah goes outside to get some more lights from the truck while Ron also goes out to relief himself. Suddenly, a strange light hits Ron who then collapses to the ground. Jonah helps him up and they go back inside to finish filming the scene. Ron is acting strangely and begins to exhibit strange behavior as he begins performing in the sex scene with Veronica, who begin screaming in pain as Jim tries to yell "cut" as Ron continues to have rough sex with her. The guys are forced to pull Ron off Veronica as he goes into convulsions and suddenly dies. T.J., Jeff, and Jonah try to help Veronica who begins hemorrhaging and she looses conciseness. They guys look over to help Ron and see that he is dead. But they also notice that Ron's legendary 10-inch penis is gone as well.
In Angel's room, she is rehearsing her upcoming scene, when the disembodied penis attacks her. Wanda walks in on this and runs out to inform Rock, Lance and Laura who run in only to find the disembodied member gone and Angel dead, with a large and gory hole in the back of her head. While everyone runs out to tell the others, Laura has an encounter the disembodied dick which attacks her.
Holding themselves up in the main cabin, Jonah, Jim, T.J., Lance, Rock, and Wanda try to make sense of what is going on, just when Laura walks in, acting strangely. After the guys carry Ron's dead body outside, they debate on what to do since they are stranded there and no one has any signal for their cell phones. Rock wants to make a run for the cars to try to get off the mountain, but when he runs outside, the disembodied penis appears and shoves itself through him. When Jonah and T.J. run outside in a futile attempt to save him, they are surprised by the appearance of a rugged mountain man, named Montz (Charles Napier) who brings them back inside to the main cabin.
Resting, Jonah and T.J. make the assumption that Ron's missing dick is possessed by some kind of alien force and is wants to use it's power to destroy and possibly do worse. Jeff suggests finding a way to kill it while Laura, who continues acting strange, wants to capture it. Lance and Wanda retreat to a nearby bathroom where he tries to calm down the growing hysterical Wanda over this unbelievable turn of events. Just then, the severed penis slithers in through an crack in the bathroom window and attacks them both.
Jonah and T.J. come up with a plan to capture the lethal creature by luring it through an open window, using a pair of women's panties borrowed from Laura, to try to trap it with Jeff's suck and squeeze device. Montz volunteers to kill it after he gives them a creepy but hilarious monologue about his encounter with a similar event back in Vietnam in the 1960s where he saw his platoon getting killed by a disembodied penis that came from the body of his commanding officer. T.J. volunteers to help out and has Jonah lock him and Montz in the kitchen to make sure that if they fail that Rock's dick will not be able to get them. But while their backs are turned, the disembodied "one-eyed monster" slithers into the kitchen and strangles Montz to death, while it shoves itself in rapid speed through T.J. killing him.
Jim panics and runs into the nearby bathroom only to find a dead and cocooned Lance and Wanda against the wall. Panicking, he runs outside to the nearby barn and tries to start a snow speeder to try to escape. But the severed penis follows him in a super-fast chase down the mountain where it knocks him off his snow speeder and then gruesomely slices him in two from the crotch to the top of the head as it burrows through the snow.
Back at the main cabin, the three survivors of Jonah, Laura, and the barely conscious Veronica are beside themselves and wait. Jonah, after being told earlier by Montz about the location of an old radio antenna atop the nearby mountain, suggests they run to a nearby cabin that Montz told them about where they is an underground passageway to the radio shack where they can travel to it and radio for help. With Veronica having regained some of her strength, they make it to the passageway, which is apparently an old mine shaft and walk through the long tunnel and make it to the radio shack where Jonah tries to get the radio to work only the severed dick follows them and lands on Laura. Jonah tries to swing at it with an axe, but the "thing" is much too fast and keeps evading his blows. Veronica then thinks of a way to fight it. She lays down on the floor and offers it to the entity which shoves itself between her legs. Veronica tells Jonah and Laura to run for safety as she will keep it occupied and use her expert thighs to drain it of it's power. Jonah and Laura flee from the radio shack cabin and down the mountain just as Veronica makes the severed dick to climax which it "blows it's load". The penis monster explodes in a massive blast, destroying itself as well as killing Veronica and blows up the radio cabin in a massive blast covering the sky with millions of particles.
Jonah and Laura seek shelter in a nearby shack where they huddle for the night. At dawn, Laura hears sounds of rain, but Jonah tells her that the rain is "Ron". The remains of the penis monster is raining down semen on the entire area.
At dawn, when the sounds had decapitated, Laura leaves the cabin and a sleeping Jonah where she ventures outside and to a place in the snow where she seems to be distraught over the death of the one-eyed monster. Laura reveals a massive bulge in her abdomen as she is now impregnated by the penis monster which attacked her earlier and will now be the apparent breeding chamber to the one-eye monster's off spring.....