It tells the story of a girl about the age of 15 who has a dark secret she is afraid to confess to anyone but her pen pal, a murderer on Death Row.

[1] Ketchup Clouds is written in a series of letters from "Zoe", her chosen alias, who lives on fiction road in England to Mr. S Harris, a criminal on death row in America.

Zoe initially starts writing to Mr. Harris specifically because she believes they must share the same guilt as, according to her view, they both killed a person they loved.

At the party she meets a 'boy [...] brown eyes [and] messy blond hair' whom she feels she has chemistry with and in which she engages in sexual activity with Max Morgan and later on, a relationship.

It is the accident that follows after he discovers Zoe and Aaron together that lead her to identify both with Mr Harris as a murderer and his unfaithful wife whom she calls a "scarlet woman" and believes she deserved her death.