Aaron: How did your son die?
Walter: Peter was very sick. I tried for a long time to find a cure, but I found it too late and he died. And I discovered an alternate universe where another version of my son was dying from the same malady. So I crossed over to the other side with the intention of bringing him back to cure him. But the frozen lake where I created a portal between universes was unsound. And when we crossed back, the ice broke and Peter... the other version of him drowned. I lost him all over again.
Aaron: And you... don't think you belong in mental institution?