A woman in her fifties dies and leaves a safe deposit box key to her two best friends (who don't know each other), with the instruction "You'll know what to do" about its contents. The box contains one passionate love letter to the woman, whose friends (and presumably her husband and daughter) had no idea of the affair. The woman's two friends, whose personalities and circumstances are as different from each other's as possible, try to figure out what their late friend would have wanted them to do, and why, and of course they disagree. Each saw only part of her, and they even called her by different variations of her name. As they work through the process, the book raises questions about the nature of friendship, love, and change. Though it's an interesting vehicle, the story seems a bit improbable to me; if the intent was for the friends to find the lover, why would she have wanted that? Yet the idea of relating in different ways to different people, showing different sides of onself, rings true.