They have always been inseparable in the public imagination, the Coen brothers, a zygotic artistic collaboration with an almost primal indivisibility. While for years Joel was credited as director and Ethan as producer, this was due entirely to a quirk in the Directors Guild of America that disallowed duel directorial credits, unless members were an ‘established duo’. This became official in 2004: they are now the established duo of commercial film – one would have to go back to Powell and Pressburger to find a cinematic partnership of such richness and breadth. With the release of Joel’s The Tragedy of Macbeth, the first film directed solely by one brother, it seems a good time to drill down into the brothers’ quintessence: what is a Coen brothers’ film, and what could or should we expect from a Coen brother film? Is the zygote finally subdividing?