Magnificent, powerful, haunting, The Changeling - a 1622 collaboration by Thomas Middleton and William Rowley - is a play that both works superbly in performance and is a goldmine for critics. It represents a paradigmatic Jacobean revenge play - with all that blood at the end, how could it be anything else? - yet it appears late enough in the development of English Renaissance tragedy both to parody the idea of revenge and to foreground the increasingly hybrid nature of the genre. It records the obtuse operations of desire in a stratified culture, mapping the spread of social pollution manifest as ugliness, the ramifications of which are apparent not only within the play but also in its critical and theatrical afterlife. Is The Changeling an ugly play, then? On one level, far from it: the elegance of its inexorability is unquestioned, whether one reads or sees it. But the physical ugliness that the play's upper-class female protagonist finds in its lower-class male protagonist, exposing and matching the spiritual ugliness she is appalled to find within herself, not only drives the narrative grimly towards hell but ramifies also in the fields of genre and of authorship. The Changeling denies its admirers the aesthetic comfort of authorial unity-of-purpose - the beauty of tragedy, as understood by generations of critics - and refuses the self-coherence, the clarity of trajectory, of the revenge genre to which it belongs. In this double rejection of singularity, the play is not perverse.