Barney Thomson, awkward, diffident, Glasgow barber, lives a life of desperate mediocrity and his uninteresting life is about to go from 0 to 60 in five seconds, as he enters the grotesque and comically absurd world of the serial killer.

In a small and conservative Scottish village, a woman’s paralytic husband convinces her to have extramarital intercourse so she can tell him about it and give him a reason for living.