In the 2010s following an economic collapse, the New Founding Fathers of America (NFFA) have taken over, instituted totalitarian rule, and reinstated themselves as the new government. Using the 28th amendment to the United States Constitution, they established one night a year—сalled "the Purge"—in which all crime is legal and all police, fire, and medical emergency services are shut down for 12 hours, from 7 p.m. to 7 a.m.
The film begins with a Broadway-style number "So Long, and Thanks for All the Fish", sung by the dolphins of the world, who are aware of the Earth's impending doom. At the end, they all jump out of the oceans and into space, leaving Earth for good.
Underneath Raccoon City exists a genetic research facility called the Hive, owned by the Umbrella Corporation. A thief steals the genetically engineered T-virus and contaminates the Hive with it. In response, the facility's artificial intelligence, the Red Queen, seals the Hive and kills everyone inside.
Two months have passed since a mutated strain of mad cow disease mutated into "mad person disease" that became "mad zombie disease" which overran the entire United States population, turning American people into vicious zombies. Unaffected college student "Columbus" (Jesse Eisenberg) is making his way from his college dorm in Austin, Texas to Columbus, Ohio to see whether his parents are still alive. He encounters "Tallahassee" (Woody Harrelson), another survivor who is particularly violent in killing zombies. Though he does not appear to be sociable, Tallahassee reluctantly allows Columbus to travel with him. Tallahassee mentions he misses his "puppy" that was killed by zombies, as well as his affinity for Twinkies, which he actively tries to find. Survivors of the zombie epidemic have learned that it is best not to grow attached to other survivors, because they could die at any moment, so many have taken to using their city of origin as nicknames, i.e. "Columbus" is from Columbus, Ohio.
After finishing a long shift, nurse Ana returns to her suburban neighborhood and her husband, Luis. Caught up in a scheduled date night, they miss an emergency news bulletin. The next morning, a neighborhood girl enters their bedroom and kills Luis, who immediately reanimates as a zombie and attacks Ana. She flees in her car but crashes and passes out. Upon waking, Ana joins with Police Sergeant Kenneth Hall, electronics salesman Michael, petty criminal Andre and his pregnant wife, Luda. They break into a nearby mall and are attacked by a zombified security guard, who scratches Luda. They are also confronted by three living guards — C.J., Bart, and Terry — who make them surrender their weapons in exchange for refuge. They split into groups to secure the mall and then go to the roof, where they see another survivor, Andy, who is stranded alone in his gun store across the zombie-infested parking lot.
A berserk motorcycle gang member named Crawford "Nightrider" Montazano (Vincent Gil), having killed a rookie officer of an Australian highway patrol called the Main Force Patrol (MFP) while escaping from police custody, is attempting to outrun the other MFP officers in a stolen Pursuit Special. Though he manages to elude his initial pursuers, the MFP's top pursuit-man, Max Rockatansky (Mel Gibson), then engages the less-skilled Nightrider in a high-speed chase. During a sudden game of "chicken", the Nightrider breaks off first, his nerve suddenly broken in the confrontation with Max; he is unable to recover his wits, which leads to the Nightrider's death in a fiery crash.
In 1944, the Nazis build a dimensional portal off the coast of Scotland. With the help of Russian mystic Grigori Rasputin, they intend to free the Ogdru Jahad—monstrous entities imprisoned in deep space—to aid them in defeating the Allies. Rasputin knows this will be an apocalyptic event that he believes will create a paradise. He opens the portal with the aid of his disciples, Ilsa von Haupstein and Obersturmbannführer Karl Ruprecht Kroenen, member of the Thule Society and Adolf Hitler's top assassin. An Allied team is sent to destroy the portal, guided by young Trevor Bruttenholm, who is well-versed in the occult. The German team is killed and the portal is destroyed—in the process absorbing Rasputin—while Haupstein and Kroenen escape. The Allied team discovers that an infant demon with a right hand of stone came through the portal; they dub him "Hellboy" and Bruttenholm adopts him.
When a massive tectonic shift triggers a tsunami capable of swallowing whole continents, the military creates an ark capable of holding only 50,000 people and the DNA of every species possible while the storm consumes most of the world.
On March 21, 2022, one hour before the annual Purge commences, James Sandin (Ethan Hawke) returns to his home in an affluent Los Angeles suburb to wait out the night with his wife Mary (Lena Headey) and their two children, 17-year-old daughter Zoey (Adelaide Kane) and 14-year-old son Charlie (Max Burkholder). James is the top salesman for elaborate security systems designed specifically for Purge night, and the family is assured that the security system manufactured by James' company will keep them safe. Their neighbors attribute the size and fittings of the newly extended Sandins' house to his success in local promotion.
In 2014, an attempt to counteract global warming through climate engineering results in an ice age that extinguishes all life except the inhabitants of the Snowpiercer, a massive train powered by a perpetual motion engine that travels a globe-spanning track, created by the transportation magnate Wilford. By 2031, elites inhabit the extravagant front cars and the "scum" inhabit the tail in squalid and brutal conditions. Under watch by Wilford's guards, they are brought only gelatinous protein bars to eat and kept in their place in the social order by Minister Mason, while sometimes small children are taken away.
In Cambridge, three animal liberation activists break into a medical research laboratory with the intent of freeing captive chimpanzees. They are interrupted by a scientist, who desperately warns them that the chimps are infected with a highly contagious rage-inducing virus that is spread through blood and saliva. Ignoring the scientist's pleas, the activists release a chimpanzee, who attacks one of them and immediately infects her — leading her to attack and infect everyone else present.
In 2065, Earth is infested by alien life forms known as Phantoms. By physical contact Phantoms consume the Gaia spirit of living beings, killing them instantly, though a minor contact may only result in an infection. The surviving humans live in "barrier cities", areas protected by an energy shield that prevents Phantoms from entering, and are engaged in an ongoing struggle to free the planet. After being infected by a Phantom during one of her experiments, Aki Ross (Ming-Na) and her mentor, Doctor Sid (Donald Sutherland), uncover a means of defeating the Phantoms by gathering eight spirit signatures that, when joined, can negate the Phantoms. Aki is searching for the sixth spirit in the ruins of New York City when she is cornered by Phantoms but is rescued by Gray Edwards (Alec Baldwin) and his squad "Deep Eyes", consisting of Ryan Whittaker (Ving Rhames), Neil Fleming (Steve Buscemi) and Jane Proudfoot (Peri Gilpin). It is revealed that Gray was once romantically involved with Aki.
Shortly after the dawn of the new millennium, during construction on the London Underground, workers penetrate an underground cave. A huge dragon emerges from hibernation, incinerating the workers with its flaming breath. The only survivor is a boy, Quinn Abercromby (Ben Thornton), whose mother Karen (Alice Krige) is the construction crew chief; Karen is crushed to death while protecting Quinn as the dragon climbs to the surface. It flies out of the Underground and more dragons appear, multiplying rapidly. Shown in newspaper clippings and a voiceover, scientists discover that dragons are a lost species responsible for the extinction of the dinosaurs by incinerating them and eating their ash, as well as ice ages. The dragons are speculated to hibernate after destroying most of the Earth's creatures until the planet repopulates. After the dragons' awakening humanity resists militarily, including a 2010 use of nuclear weapons; this, however, hastens the destruction and within a few years humans are nearly extinct.
On May 12, 1984, two beings from the year 2029 arrive in Los Angeles: one is a Terminator T-800 Model 101, a cyborg assassin programmed to kill a young woman named Sarah Connor; the other is Kyle Reese, a soldier sent to protect her from the T-800. After the Terminator kills a gang member, a gun-shop manager, the two other women named "Sarah Connor" listed in the telephone directory, Sarah's roommate Ginger, and her partner, it tracks its target to the Technoir, a nightclub. Kyle arrives and saves Sarah from the Terminator. The two steal a car and escape, while the Terminator steals a police car and pursues them.