Shaun Riley is an appliance salesman who is going nowhere in life; he follows a mundane routine, and his girlfriend Liz is dissatisfied with their relationship, primarily because it revolves around going to "The Winchester", Shaun's favourite pub. He also has issues with his hated stepfather Phillip, his increasingly unhappy flatmate Pete, and a dissatisfying job where his younger co-workers show him no respect. Following a broken promise to do something special for their anniversary, Liz dumps Shaun. Shaun decides to drown his sorrows at the pub with his other flatmate Ed, his best friend. After a night of drinking, he has an epiphany and resolves to sort his life out.
Unfortunately, this revelation comes at the same time as an uprising of the undead, who begin to attack and devour the living. Shaun comes to realise the gravity of the situation after having a close shave with a zombie. Shaun, along with Ed, proceeds to rescue his loved ones, deciding to take Liz, along with Shaun's mother Barbara, Phillip, and Liz's friends David and Dianne, to the Winchester Pub to survive the plague.
During their journey, Phillip is mortally wounded but manages to make his peace with Shaun before turning into a zombie, forcing the group to abandon him, and their car, and go the rest of the way on foot. The remaining group find the Winchester surrounded by zombies, but Shaun manages to draw the undead away while the others barricade themselves inside. Shaun returns to the pub thinking that he gave the zombies the slip, but the zombies followed him, and soon break in. Barbara is shot by Shaun after becoming a zombie, David is torn apart and eaten, Dianne charges outside in a vain attempt to save David, Ed decides to stay behind after being bitten, and Shaun has a final confrontation with a zombified Pete. Shaun and Liz, who have reconciled over the course of the day, prepare for one last great battle against the zombie horde, but are saved by the British Army.
Six months after the zombie outbreak, society has returned to normal, and zombies have now become a part of everyday life, being used as cheap labour and game show participants. Shaun and Liz move in together, along with undead Ed, who 'lives' in the garden shed

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