The Night Heron, Royal Court Theatre, London

Seven years ago, Jez Butterworth's Mojo stirred banality and evil into a sizzling comedy that made critics hail the debut of an extraordinary new writer. His second play – in the interval he has been busy with films – offers the mixture as before

The Night Heron doesn't have the excitement of its predecessor but it's a quirky, creepy play with scenes few other writers are likely to imagine. Not many, I think, would have a lynch-mob of religious maniacs confounded by a naked boy reciting Shelley.

Instead of the hysteria and violence of Mojo, the mood here is nervous dread. Like all of us, Griffin and Jess have been cast out of the garden, but they have also been literally evicted from it. Former gardeners at a Cambridge college, they live in a decrepit fenland cabin, eating rabbits when they can catch them.

Their new lodger is an ex-con, perhaps a witch, and Jess is being blackmailed by a puppy poisoner. Small wonder that the visitors seeking a glimpse of a rare bird aren't the only twitchers about. But the chaps have an idea that will solve all their problems: they will win a poetry contest.

Butterworth sets up a nice odd-couple by-play between the unworldly Jess and Griffin, a hearty, practical type who proves unequal to circumstances. The disruption of their menage by the rough, intense Bolla is funny even without her habit of making unanswerable remarks, such as "I know where your arteries are''. But there's too little action too late, and too much talk, which is merely strange rather than suspenseful. Also, too little of it can be understood unless one is fluent in East Anglian Rustic or South London Yob.

An "ass-warming'' is not what happens when one stands in front of a fire but a party for a new home, and "mash'' is not what one does to potatoes but a wet place where the long grass grows. The uncertainty of whether the men are villains or victims isn't sufficiently pointed, and the danger never feels real or near enough.

Even Jess's involvement in a cult called the Sons of the White Prince never amounts to much – the visit of the mob and Jess's sudden decision to play Christ simply fade away.

A normal-sized, nice-looking woman, Jessica Stevenson is an odd choice for the eerie, bulky Bolla, whom she plays as if giving an imitation of a truck driver. But the rest of Ian Rickson's cast splendidly embody these characters you wouldn't want to meet on a dark fen, especially Ray Winstone's ostensibly sane Griffin.

Paul Ritter contributes a priceless cameo as the copper who is ever helpful – such as when he offers to have "a word in a few of the appropriate shell-likes'' – but can't recognise trouble until it threatens to cut his arteries out.