Winter, 1916. In St Petersburg, snow is falling in a country on the brink of revolution. Beautiful and headstrong, Sashenka Zeitlin is just sixteen. As her mother parties with Rasputin and her dissolute friends, Sashenka slips into the frozen night to play her role in a dangerous game of conspiracy and seduction. Twenty years on, Sashenka has a powerful husband and two children. Around her people are disappearing but her own family is safe. But she's about to embark on a forbidden love affair which will have devastating consequences. Sashenka's story lies hidden for half a century, until a young historian goes deep into Stalin's private archives and uncovers a heart-breaking story of passion and betrayal, savage cruelty and unexpected heroism - and one woman forced to make an unbearable choice.