When a loved one dies we mourn our loss. We take comfort in the rituals that mark the passing, and we turn to those around us for support. But what happens when there is no closure, when a family member or a friend who may be still alive is lost to us nonetheless? How, for example, does the mother whose soldier son is missing in action, or the family of an Alzheimer's patient who is suffering from severe dementia, deal with the uncertainty surrounding...