Set in Beijing the novel focuses on a taxi driver, Wang Jun, who begins receiving ominous letters from someone claiming to be his re-incarnated soulmate who has known him over six previous incarnations.
According to Barker she spent six years completing the novel which was written as she lived in Beijing, Seoul, Colorado, Boston, Leeds, Washington DC, London and Shenzhen.
Jun continues to find letters in his cab with the mysterious writer telling him that they have met before in previous incarnations.
Each letter takes places in a different historical time period and they frequently involve violence, same-sex relationships and betrayal.
His mother, Li Shuxiang was deeply mentally ill and eventually died of drowning by swimming in a polluted river.
During their fight Ling Hong reveals that Li Shuxiang actually lived years beyond what Jun was told though she eventually died after returning to her hometown.
The final letter is set in 1966 and tells the story of Yi Moon, the teenage daughter of a political dissident who has an affair with Zhang Liya, a well-connected and privileged member of the communists.