'Theatre is littered with sister double acts: Antigone and Ismene, Kate and Bianca, Blanche and Stella, Fleabag and Claire. The shared history of sisters delivers inbuilt emotional stakes and lots of baggage. The doubling of experience brings both love and rivalry, the joys of being known and the horrors of being trapped by the reflection of the other. Looking like not-quite twins, real-life sisters Hayley and Mandy McElhinney are the dirty birds of the title, in the world premiere of a co-written work in which they play reclusive sisters.' (Introduction)