The film, written by Stallone, was loosely based on a novel Fair Game by Paula Gosling, which was also filmed under that title in 1995; it also arose out of Stallone's original ideas for the film Beverly Hills Cop. Cobra was a modest hit at the box office and cult favorite, but was widely panned by critics for its cartoonish violence and cliched plot.
Marion Cobretti (Stallone), a rough Police officer part of the "zombie squad" with a reputation for doing "the dirty work" is called in to a hostage situation at a grocery store when negotiations fail. Cobretti kills the gunman himself after infiltrating the building, but before his death the criminal mumbles of a "New Order" in the world: a group of supremacists who believe in killing the weak and leaving only the strongest and themselves to live and rule the world.
The event at the supermarket is connected to a string of recent and seemingly unconnected acts of violence that have broken loose in Los Angeles. Unbeknownst to the general public, these murders are the work of the same supremacist group that the supermarket gunman spoke of.
After witnessing several individuals (and the Order's leader) at the scene of one of the murders late at night, Nielsen's character becomes the target of the group, and the only witness to their crimes. She is placed under the protective custody of Cobretti and his partner. After several attempts are made on their lives, it is decided that it would be safest that they relocate from the city.
Shortly after venturing out into the countryside, Cobretti becomes romantically involved with the witness. One of the Order's leaders (who was also a police officer) then reveals the location of Cobretti, the witness, and Cobretti's partner. The Order sieges the small town that the three were staying in. Cobretti and the witness escape in a Dodge Ram pick-up truck assuming his partner is dead. After the truck becomes severely damaged, the two bail out into a lemon grove and escape into a nearby factory. Most of the Order has been killed or disabled by Cobretti at this point, and only few follow them. After eliminating every member aside from the leader, The Night Slasher, a huge muscle bound type played by Brian Thompson, Cobretti and the leader engage in a hand-to-hand duel inside the steel mill, ending with the Order's leader being impaled and burned alive by Cobretti.
In the aftermath, Cobretti's department has arrived and begun clean-up of the town, the Order is all but eliminated, and the ending credits begin with Stallone and Nielsen climbing onto one of the many motorcycles left by the Order and riding away.
Ocean Software released a video game in 1986 to coincide with the film's release. The game a side-scrolling action game where the player controls Cobretti as he tries to defeat the cult of the Night Slasher and protect model Ingrid from their wrath. Released for the Commodore 64, ZX Spectrum, and Amstrad CPC, the game is well-known for its music score and its high level of difficulty. The music is arranged by Ben Daglish. Due to a rush to get the game out in time for the film's release, there was no final boss programmed in to end the game; Once the first three levels are completed, the game repeats.