On a freezing January morning in 1961, eight-year-old Anna's mother disappears into the fog. That same morning, a spy case breaks in the news. Obsessed by stories of espionage, Anna's brother Peter begins to construct a theory that their mother, a refugee from eastern Germany, was an undercover spy and might even still be alive. As life returns to normal, Anna struggles to sort fact from fantasy. Did her mother have a secret life? And how do you know who a person was once she is dead?