Death and Dread

As children we never think that our pet will go away sometime. As children pets, like our parents, are immortal. They can do any trick, out run any critter, fetch any ball. Eventually though, they do die, and we have to face the harsh reality that is death.
I feel that it is almost impossible to explain death to a child.

"Where is (_____)?
"They died."
"When are they coming back?"
"They aren't coming back."
"Don't they want to be with me?"
"Yes sweetheart, but they can't."
"But if they want to then why don't they just come back?"
"It doesn't work that way honey."

I can honestlly say I dread having this talk with my daughter.