Marnie FitzPatrick is a reclusive sixth-former from Hertfordshire with a dysfunctional family, a penchant for Pythagoras' theorem and an addiction to doughnuts and gin. Julie Crewe is a disillusioned maths teacher who lives vicariously through the girls she teaches, yet who once danced barefoot through Central Park with a man called Jo she has never been able to forget. This is the story of what happened in the summer of 1969, when the sun burned down on the roof of the Shredded Wheat factory, and a boy called Freddie Friday danced to the records he had stolen. This is about first love and last love and all the strange stuff in between. This is what happens when three people are bound together by something that can't be calculated or explained by any equation. This is what happened when they saw the open door.