The passion and pathos of legendary poet Dylan Thomas (Matthew Rhys) is told through the lives of two extraordinary women. Vera Phillips (Keira Knightley) and Dylan were each other's first loves who feel the thunderbolt once more when they unexpectedly meet in London ten years later. Caitlin (Sienna Miller) is his adventurous wife, wily at using her beauty and always up for a bit of fun.

Despite their love-rival status, the women form a surprising friendship - and though bombs rain down on London, the trio indulge in the glory of being young, and alive. When Vera meets and marries handsome Officer William Killick (Cillian Murphy), Dylan resents his trio becoming a foursome - and Caitlin notes it.

The collapse of their group is avoided when William gets sent away to war - and the others move back to rural Wales. With Vera now heavily pregnant and missing a husband who never writes back, the battle between her heart and head becomes more intense. William's return instigates a confrontation that has long been brewing - but the savagery of his attack on Dylan finally forces Vera to choose between the men in her life and the friend that she loves.

Desire and guilt are complicated by love and friendship in this real-life tale set in beautiful London and the majestic Welsh countryside.