George A. Romero’s zombie saga takes an unexpectedly Irish turn in this final chapter they should have called St. Patrick’s Day of the Dead.

In a first for the franchise, Survival of the Dead retains a character from the previous instalment, following a soldier (Alan van Sprang) who popped up briefly in Diary of the Dead. To escape the zombie outbreak, his squad flees to an island off the coast of Delaware, exclusively populated by Irish people for some reason.

The island is divided into two families at war over how to control the local zombie population. Patrick O’Flynn (Kenneth Welsh) favours the more rational “kill them all” option, whereas Seamus Muldoon (Richard Fitzpatrick) is training the undead to eat animals other than humans; a plan so brainless even the ghouls know it’s stupid, not least because it risks turning all your livestock into zombie pigs and horses.

That would have actually been more entertaining than this unfortunate endpoint to such a monumental series. After 40 years Romero had done everything one could with zombies, and apparently had nowhere left to go apart from bizarre Irish soap opera. At least Diary of the Dead had modern social commentary; the closest this entry comes to an allegory is the sad image of a zombie tethered to a post swaying disinterestedly at a pig, an apt metaphor for a franchise at the end of its rope.

Romero’s greatest strength as a director was his vision; with each instalment he imagined the next phase in post-apocalyptic society. And while Zombie Western is a likely enough scenario (The Walking Dead got 11 seasons out of it), the execution is muddled and anachronistic. It relies awkwardly on silly drama and acting, instead of the realism and political ideas that Romero brought to horror movies – and brought them back.

His 2009 effort finds any hint of commentary around war or vegetarianism overshadowed by irritating characters, cheap CGI and cringey dialogue: “You’re dangerous kid, but not as dangerous as me.” That said, Romero does land some deadpan one-liners, including the character who sees a zombie attempt to drive a car and says, “He’ll never pass his test.”

Overall though it is disappointing to see arguably the most influential horror franchise of all time end not with a bang, or a whimper, but with the image of a zombie eating a horse. It leaves you feeling that Romero should have called it a day after Day, and switched to directing Iceland adverts.