London couple Sarah (Shirley Henderson) and Tom (Alan Tudyk) are in deep financial trouble. Their situation takes a terrifying nosedive with the shocking behaviour of uninvited dinner guest, Jessica (Indira Varma). Faced with the moral dilemma of their lives - and dragging their best friends Richard (Rufus Sewell) and Beth (Olivia Williams) with them - they make a series of choices that could either be their salvation or destruction.