William Woolf is a letter detective at the Dead Letters Depot in East London, spending his days reuniting lost mail with its intended recipient. But when he discovers a series of letters addressed simply to 'My Great Love' everything changes... Written by a woman to a soulmate she hasn't met yet, her heartfelt words stir William in ways he has long forgotten.

Could they be destined for him? And what would that mean for his own troubled marriage? William must follow the clues in the letters to solve his most important mystery yet: his own heart.