A Place in the Hills by Michelle Paver

Antonia had become obsessed with a long-dead poet, Cassius. A soldier and lover, he had lived in the hills of Provence in Roman times where Antonia was now engaged in an archaeological dig. Her father was hoping to uncover a Roman villa, but Antonia had more romantic hopes - she longed to solve the riddle of Cassius, a secret contained in one of his poems. With her on the dig is Myles, her boyfriend from university days, and his fascinating friend Patrick -who also wants to uncover the mystery of Cassius's riddle. When they find an unimaginable treasure in a remote hillside cave Patrick and Antonia also discover an electric attraction between them.

But tragedy strikes the dig, and Antonia and Patrick are parted. The treasure vanishes and it seems that the mystery will never be solved. Until many years later, when a wholly unexpected development means a new start.