London in 1934. Clever young civil servant Doreen Bates is working in the same office as E, an older married man. In the years just before the war, they develop an irresistible attraction to one another and strike up a passionate affair. Doreen records it all with startling candour in her diary - secret midnight walks, countryside escapades and stolen moments of intimacy.

But Doreen starts to long for a child with E. Despite all the taboos of the time, and against the wishes of E, she is determined to become a mother - even though she knows that her decision will provoke anger and shame from her family, friends and colleagues. Eventually she gets pregnant and is amazed when twins are born during the war. However, Doreen faces an uncertain future - will E ever leave his wife and join his new family?

This is the story of a young woman forging her own path in a period of turbulence and uncertainty.