Gary King, played by Simon Pegg, is a middle-aged man grappling with his past as a recovering drug addict. Determined to reconnect with his estranged school friends, he embarks on a nostalgic quest to complete the "Golden Mile", a legendary pub crawl that spans twelve pubs in their hometown of Newton Haven. This adventure is rooted in their teenage years when they attempted the crawl but were unable to make it to the final pub, the World's End.
Accompanied by his friends—Peter Page, Oliver "O-Man" Chamberlain, Steven Prince, and Nick Frost—Gary returns to Newton Haven. At their second stop, The Old Familiar, they are unexpectedly joined by Oliver's sister Sam, portrayed by Rosamund Pike, with whom both Gary and Steven have shared past romantic tensions. Attempting to reignite these sparks, Gary's advances backfire spectacularly when he tries to proposition Sam in the ladies' room, leading to a swift slap that underscores the awkwardness of old flames.
Things take a bizarre turn at the fourth pub, The Cross Hands, when Gary finds himself in a showdown with a surprisingly strong teenager, revealing that not everything is as it seems when the boy's head gets knocked off, disclosing him as a robot. The friends join Gary in the ensuing chaos, battling these mechanical foes. That's when Andy, initially abstaining from alcohol, can't resist the temptation any longer and indulges in some shots.
As they forge on through various establishments, they encounter Sam again, and Gary feels compelled to warn her about the robot invasion. After several attempts to convince her, she's finally swayed when he heroically saves her from twin robots posing as their friends. At The Mermaid, seductive robots aiming to steal their DNA lead to increasing tension when Sam is reminded of her late childhood crush, Adrian, causing her to panic.
Upon reaching the ninth pub, The Beehive, they encounter Guy Shepherd, played by Pierce Brosnan, who encourages them to surrender to the inevitable and accept being replaced by robots. An alarming realization hits Andy when he notices Oliver has been swapped out for a robot. Following a confrontation, the group starts to suspect each other of being replaced. In a desperate attempt to prove his humanity, Gary resorts to self-inflicted pain, much to the dismay of his friends.
As chaos reigns, Peter gets captured by the automata, but steadfastly, Gary insists on completing their journey. The final destination, The World's End, sees an intense confrontation between Gary and Andy, where a shocking revelation of Gary's troubled past resurfaces—his bandaged wrists reveal a suicide attempt.
When they descend into the unexpected hidden chamber below the bar, they face the Network, an alien entity responsible for the invasion. It offers them immortality through transformation into robots, yet they resist, fueled by a fundamental belief in the freedom of humanity. Ultimately, the Network concedes defeat and the invasion is halted. In a dramatic escape, Sam arrives to rescue the remaining group as Newton Haven begins its self-destruct sequence.
In a reflective campfire tale set against the backdrop of post-apocalyptic London, Andy shares their ordeal, detailing the worldwide Electro-Magnetic pulse that dismantled modern technology and thrust humanity back to the Dark Ages. Relationships have mended among the survivors, with Andy's marriage thriving, Steven and Sam together, and robotic resemblances of Peter and Oliver returning to their previous lives. In the remnants of Newton Haven, Gary finds himself entering a pub, now sober, where he orders a round of water, echoing his spirited introduction to the Golden Mile, before drawing a sword and leading his fellow robotic friends into a raucous brawl.
