According to legend, when Pandora's box is opened it unleashes dark secrets and terrible consequences ... Rachel Wetherby's life has been on hold since the diagnosis of her teenage daughter Shelley with a debilitating - and fatal - illness. So when Rachel's mother offloads a box of her old possessions, including a diary, Rachel feels compelled to escape into a past which - on the surface - was care-free. However, opening up the box unearths secrets and memories best left uncovered. Shelley, meanwhile, is juggling a secret romance with planning her own death. Convincing Rachel that she'd like to spend her 15th birthday in Cornwall where she spent so many idyllic childhood summers, she devises her plan. But nothing is as it seems and heartache and surprises lie in store for both mother and daughter.