In the exceptionally dark British comedy Sightseers , a nondescript couple takes its first trip together, traveling the British countryside while having sex, bickering and, oh yes, committing a series of murders. If Terrence Malick's Badlands springs to mind, let it spring right out again. Sightseers is one of those strange comedies in which a sense of uneasiness is accompanied by chuckles and in which audaciously violent acts are committed by two people who look as if they might find participation in a cribbage game a bit too stressful. Working from a screenplay by Alice Lowe and Steve Oram -- who also star in the movie -- director Ben Wheatley adds a perverse wrinkle to the idea that it's impossible really to know someone until you make a long car with them. Wheatley presents this journey in a flat, uninflected style that enhances its humorous aspects, but he doesn't skimp on showing us the murders, one of which is carried out when a man is repeatedly and viciously beaten with a stick. The couple's victims -- a litterer, among them -- are guilty of some of the annoying things that irk many but drive few to violence. The generally unimpressive Chris instigates the rampage as he and Tina make stops at northern British attractions that fall a tad short of wondrous, a pencil museum, for example. It's possible to see Sightseers as an extreme look at what happens in a relationship as people reveal themselves, and if Oram and Lowe seem comfortable in these oddball roles, it's probably because they've played these characters before, once in a rejected sitcom pilot. Wheatley builds toward a mordant punchline that puts a fitting topper on this weird road trip, but if you step back from Sightseers, it may reveal its own slightly discouraging truth: The better you get to know it, the more it seems like a limited, one-joke movie.