Anyone who's lost a family member knows the feeling of unreality that follows. Psychologists call it "denial," but it's something more than that — it's a sense that you're not really there, that you're living in an alternate world, that the pain you're feeling can't possibly be real. Grief is a powerful thing, and it can temporarily turn people into walking ghosts.
Or, as Dana Cann writes in his debut novel, Ghosts of Bergen County: "This was life: you're here. And this was death: you're not. And then you're here again, haunting some stranger. And none of it matters."