Stranded in Rome, with all planes grounded due to volcanic ash, Callum gratefully accepts a lift back to London with a friend-of-a-friend who's on her way home after a European road trip in a campervan.
But when he meets her, his heart plummets - she's Emma, his ex, The ex, and he can't be stuck in a van with her.
When Emma sees Callum again, she's horrified. It's taken so many years to heal her heart - she really doesn't want to spend the next few days in close quarters with him.
As they embark on the drive of a lifetime, it begins to feel as though fate might have had a hand in reuniting them. But understanding what happened in the past and coming to terms with the present isn't easy.