⋆⋆⋆ out of four stars

The murder spree “Sightseers” turns a quiet camper trip through the British countryside into a comically macabre walk on the wild side. It’s a truism that comedy often deals in pain, and many jokes are forms of aggression lightly disguised. The best way to appreciate this briskly paced sick joke is to view its multiple fatalities as especially pointed examples of slapstick.

Co-written by its stars, sketch performers Alice Lowe and Steve Oram, the film melds morbid material with observational comedy and stiletto-sharp character humor. Tina, a dowdy 34-year-old who lives with her guilt-tripping mum, breaks free for a driving holiday with her fellow dullard, Chris. With his thinning rusty hair, full beard and nondescript windbreaker, he may be England’s most unremarkable man. The vacationers’ itinerary includes several of Yorkshire’s dumpiest tourist attractions. They happily gawk and pose for pictures at the Crich Tramway heritage site, the Keswick Pencil Museum, and the Ribblehead Viaduct. The film quickly establishes a deliciously mundane tone akin to Nick Park’s Wallace and Gromit animations. But wait. There will be blood.

When an accidental (but wish-fulfilling) fatality befalls a litterbug who sullies an antique trolley, Chris inflates a bit. The tedium lifts. This colorless, peevish fellow, clearly a lifelong fall guy, experiences a moment of caveman triumph. Invigorated, he begins to make good on his wry boast that their trip will be “an erotic odyssey.” The camper starts a-rockin’. Chris begins to lash out for insignificant frustrations. The body count mounts. Feeling competitive, Tina tries her hand. She proves even more adept, causing Chris to double down. Soon news bulletins announce that the police are seeking a ginger-faced man and an angry woman.

The joke here is how completely Chris and Tina embody the banality of evil. We get to know them — daydreams, insecurities, social tics and all. Other than their outbursts, they’re uproariously dull. Lowe and Oram underplay to perfection, Eileen Davies is a howl as Tina’s passive-aggressive mother, and director Ben Wheatley infuses the film with sly wit. The quick pitch on this one is “Wes Anderson meets ‘Natural Born Killers.’ ” If that doesn’t snag you, move along, nothing to see here.