In the rainswept summer of 1968, Rose sets off for the United States from Kentish Town to meet a man she knows as Washington Harold, in her suitcase a polka-dot dress and a one-way ticket. In a country rocked by the assassination of Martin Luther King and a rising groundswell of violence, they are to join forces in search of the charismatic and elusive Dr Wheeler - oracle, guru and redeemer - whom Rose credits with rescuing her from a terrible childhood, and against whom Harold nurses a silent grudge.

As they trail their quarry, zigzagging through America in a camper van, the odd couple - Rose, damaged child of grey postwar Britain, and nervous, obsessive, driven Harold - encounter a ragged counter-cultural army of Wheeler's acolytes, eddying among dangerous currents of obscure dissent and rage. But somewhere in the wide American darkness, Dr Wheeler is waiting.