Ed has been Shaun's best friend since childhood. Content to play video games and crash on Shaun's couch, Ed's sloth is usually rubbing off on the malleable and dissatisfied Shaun. But while neither friend is the most driven fellow, the two friends are forever linked and loyal to one another. When Shaun's life takes a downward turn, Ed does all he can to push Shaun to lighten up and have a little fun.

After Shaun has a terribly unsuccessful day, complete with being dumped by his girlfriend Liz, Ed commiserates with his best friend as they drown their sorrows at The Winchester pub. Despite Ed's advice to move on and forget Liz, Shaun drunkenly realizes that his miserable and mundane routine will never make him happy. Shaun vows to get Liz back, reconcile with his parents, and make something of his life. Meanwhile, a zombie plague threatens to overtake London and ruin Shaun's plans and Ed's busy schedule of playing video games. In order to save their futures, Shaun and Ed round up Shaun's friends and family, and they make the epic journey back to the pub to fight off the undead from the bunker of The Winchester.