Summer, 1914. Clara, a passionate young London wife and the mother of two small girls, is married to Henry, a manager at an insurance company, but the marriage is not in good shape. Both of them have, in their own ways, given up on it.

As the countdown to WWI begins in the capitals of Europe and war is declared, Clara discovers Henry is having an affair with a woman at work. Clara too finds herself drawn to another man, James, a divorced Foreign Office worker, and must fight against both the conventions of the time and her own conscience as they fall in love. But when Henry and James enlist, Clara must begin the long vigil, waiting to see which, if either of them, will return from the fighting.