Walking home on Bonfire Night, Samantha Adams Jodie Whittaker, a 25-year-old trainee nurse, finds herself the victim of a mugging by a group of teenage delinquents led by Moses John Boyega. The gang includes Pest Alex Esmail, Dennis (Franz Drameh), Jerome (Leeon Jones), and Biggz (Simon Howard). Their criminal escapade is abruptly interrupted when a meteorite crashes nearby, providing Samantha with a chance to escape.
Curiosity leads Moses to investigate the wreckage of the car that was struck. In a twist of fate, he encounters a strange, pale creature that emerged from the meteor, causing an injury to his face. As the gang pursues and ultimately kills the creature, they decide to capitalize on their find and seek advice from their acquaintance, cannabis dealer Ron (Nick Frost), who resides at the top of the Wyndham Tower. As the group gathers to form a plan regarding the alien remains, they are unaware that more extraterrestrial objects are plummeting from above.
When larger and more menacing creatures appear—mysterious, gorilla-sized beings that are covered in shiny, pitch-black fur—the gang’s bravado is put to the test. After a chaotic sequence of events leads to Moses being recognized as a criminal by Samantha, the group finds themselves besieged by the very aliens they sought to confront. As they escape, the danger multiplies; police officers encounter the aliens, leading to a shocking sequence where the police are brutally massacred, leaving Samantha and Moses in a precarious situation.
Trying to regroup, the gang makes their way to Wyndham Tower, but finds themselves relentlessly pursued by the fearsome aliens, resulting in more injuries and unexpected losses among their ranks. In a desperate bid for survival, they invade Samantha’s flat seeking sanctuary, where she ends up confronting the threat head-on when an alien barges in. Armed with a samurai sword, Moses becomes their protector. Understanding that they must unite against a common enemy, Samantha chooses to stick with the gang, realizing that together they stand a better chance of survival.
As the aliens continue to assault their hideouts, the gang attempts to reach Ron’s fortified flat. However, they face increasingly deadly confrontations, leading to the deaths of some members. The tension escalates when Moses, now armed with a significant plan of action after Brewis (Luke Treadaway), a zoology student, theorizes about the aliens’ reproductive strategy, decides they must leverage the mating pheromones that the smaller alien left on him.
With a daring plan set in motion, Samantha, untouched by the pheromones, takes a risk to turn on the gas in Moses’ apartment in hopes of thwarting the alien threat once and for all. As chaos ensues, Moses, now weighed down by the dead creature, successfully lures the larger males into the gas-filled flat, igniting a massive explosion that presumably eradicates the threat.
In the aftermath, however, the remaining gang members are apprehended, facing accusations for the destruction and deaths around the block, including the two cops that had earlier detained Moses. Yet, amidst the turmoil, Samantha rises in their defense, acknowledging their bravery and intent to survive. In a bittersweet end, cheers erupt from residents of the block in support of Moses and his crew as they ride away in police custody, hinting at their unexpected heroism amidst a night of terror.
