Friendship is like a shark: it has to keep moving forwards to survive.

Esther and Laura have been best friends since they were seven, when Esther was chubby and Laura was already perfect. So much has changed since then - school, boyfriends, drink, experimental hair-dye, university, jobs, London, babies - and their friendship has changed just as much, but they are still close, still inextricably linked to one another.

So when Esther is told that Laura has gone missing, she leaves everything behind - including her husband and small child - to fly to San Francisco and trace her friend's last movements. All she has is an email from Laura: 'I'm channelling Drew Barrymore, as ever. The Gospel, right?'

In trying to understand why Laura has disappeared, and what on earth Drew Barrymore has to do with it, Esther needs to look back. Back at the secrets woven into their friendship and the truths she's avoided facing for so long.