1975. Helen O'Dowd and Sarah Flannery encounter one another briefly, under traumatic circumstances. 3 years later their lives collide unexpectedly again, and for the next 30 years they remain in contact without ever laying eyes on one another. As time goes by they share their triumphs and disasters, their hopes and their fears. This is the story of their friendship - from its traumatic beginning to its most unforeseen end.