A group of humans arrive on Sirius 6-B to investigate an SOS signal sent out from the planet, which has been supposedly deserted since the destruction of the man-made weapons known as "screamers." Once the squad arrives, they find a group of human survivors eking out an existence in an old military outpost, but more important, they discover that the threat of the screamers has become even more insidious, now that they're able to morph into human form.

July, 1995, the time is out of joint. Two teen girls, Sam and Corey, have left Virginia for L.A. to start over. Sam's brother has died and her family's shattered; Corey's too wild. They have car trouble in a small desert town, where Corey immediately starts her partying ways, where a meteorite strikes a windmill, and where a burned-out Desert Storm vet predicts the end of the world in four days. Sam hallucinates while sleepwalking, young men have disappeared from town, and cars come out of nowhere to cause accidents. Time travel may be possible, but it takes courage and resolve. Is the addled war veteran right? If he is, can Corey or Sam make things right?

Sam Reide has the ability of traveling to the past and works to the police department solving unresolved crimes, witnessing the events with the support of his sister Jenna Reide and reporting the criminal's identity to Detective Dan Glenn. When Elizabeth Brown that is the sister of his former girlfriend Rebecca Brown that was murdered a couple of years ago pays a visit to him, she tells that she has just found Rebecca's journal with evidences that Lonnie Flennons, who was accused for the murder, is innocent. Sam decides to witness the murder of Rebecca and his interference affects the future. He travels to the past other times trying to fix his mistakes, but every time he returns, the future is in worse condition.

Picking up immediately where Anaconda 3 left off, herpetologist Amanda Hayes finally learns her employer Murdoch's true colors when he hires a doctor to harvest a fresh supply of blood orchids to experiment with the regenerative nectar on a baby snake in order to seek treatment for his own terminal illness. Amanda is forced to secretly bring together another team of scientists whom face off against a heavily armed squad of Murdoch's men to steal the coveted orchids before the killer Anaconda hunts both parties down.

When most of the population of Earth is infected with a virus and transformed into flesh eaters and blood drinking creatures, a group of hunters led by Tao chases the vampire zombies to eliminate them. Six non-infected survivors try to find the exit of an abandoned hospital crowded with the infected creatures, and Tao and his group help them. Meanwhile, the military command is ready to bomb the area and wipe it from the map.

When his father's body is stolen from its grave, Afro takes up his sword again to tear through an army of deadly foes led by a sadistic leader.