It's the late 19th century and Emmanuelle Sonnenschein (DAVID DE KEYSER) is a Hungarian Jew who's built a family fortune from a passed-down recipe for an elixir known as "A Taste of Sunshine." With the help of his wife, Rose (MIRIAM MARGOLYES), he's also raised his two sons, Ignatz (RALPH FIENNES) and Gustave (JAMES FRAIN), and their cousin, Valerie (JENNIFER EHLE), to be fine young people. Thus, Emmanuelle's pride is hurt when neither of his sons wishes to continue the family business.
Things become even more contentious when Gustave, a doctor in training, announces that he knows of the love between Ignatz, an aspiring lawyer, and Valerie, a budding photographer, despite them being related. The two eventually marry and have children, the three young adults change their last name to Sors in the belief that it will help their aspirations, and WWI eventually breaks out, all creating more tension in the family.
With time and various characters passing on, Ignatz and Valerie's sons, Adam (RALPH FIENNES) and Istvan (MARK STRONG), are young men with Adam soon becoming a star fencing champion for Hungary during the 1930s. Faced with the same anti-Semitism his father faced, Adam decides to convert to Christianity so as to join a prestigious officer's club and further his fencing career. During his conversion, he meets Hannah Wippler (MOLLY PARKER), a woman who's not only similarly recently converted, but also engaged to another man.
Despite her pending marriage, Adam eventually wins her over and they marry and have children, just like Istvan and his new wife, Greta (RACHEL WEISZ). Things seem great for the families as Adam heads off for the Berlin Olympics, but a later affair and the outbreak of WWII changes everything, especially since the families - no matter their efforts - can't escape their Jewish pasts.
After the war and its devastation on the country and its people, Valerie (ROSEMARY HARRIS), now an old woman, returns home as does Adam's son, Ivan (RALPH FIENNES). Having seen the atrocities committed during the war, Adam soon joins Andor Knorr (WILLIAM HURT), a communist official heading a witch-hunt of sorts looking for Hungarians who assisted the Nazis during the War.
Beginning a covert affair with Carole Kovacs (DEBORAH KARA UNGER), a policewoman married to a powerful political hero, Ivan soon finds his world being turned upside down as political upheaval, family secrets and changes of fortune alter his life and make him reflect on the history of his family in Hungary.