Edward Feathers has retired to Dorset after a booming judicial practice in Hong Kong. Born in Malaya to a British father and a local (who passes away immediately after Edward's birth), Edward's life has revolved around his search for "home". Sent to Britain as a young boy to be raised under the tutelage of his father's sisters (who show no interest in him), Edward finds himself in a boarding school where the personal attention of the benevolent "Sir" and the promise of a family during holidays helps him to define his identity and dissipate the ghosts of his birth and early childhood.
The Filth in the title comes from the acronym :Failed in London, Try Hong Kong, referring to Edward's success as a lawyer and subsequent judge in Hong Kong after trying pennilessly for many years to break into the British law scene. Gardam mentions on the novel's first page that this is not intended as irony given that Edward was very particular about personal hygiene.
Throughout the novel, from Edward's painful childhood to the adolescent journey on water that will transform his life to his later marriage to Betty and professional success, Gardam moves back and forth in time to develop a complete portrait of Filth's isolation. A large part of the novel is set after Betty's death, when Edward, utterly at loss on the ways of living, decides to connect to his past. He visits his cousins and makes trips to places he remembers from his childhood. But none of this can return him to the certainty of life with Betty and ultimately he decides to leave England to make one last trip to the East, where right after getting off the flight, he passes away in a rush of happiness triggered by the freedom that a willingness to die gives.