bedtime worries

Lately my son (N) has been worried at night.
After I turned out the lights and tucked him into bed on Tuesday he asked, "What happens if an earthquake comes while I’m asleep and I die? What happens if you and Dada die?" We had just read a book called "Meteor" by Patricia Pollaco, which is a fun book in which nobody gets hurt, but which reminded him about earthquakes, and so we explored many questions of earthquake safety and existential angst.

Last Night I tell him I have to go do our taxes and he asks, "What happens if you and Dada go to jail?" I realize we had read, "Henry Climbs a Mountain" the week before. This is a cute picture book about the time Henry David Thoreau was thrown in jail for refusing to pay his taxes to a state that allowed slavery.
Me: I would call your uncles and aunts, and they would take care of you until we got out. But we're not going to jail
(N) What if they were all sick?
Me: Then we'd call your grandparents (I name them one by one)
(N) What if they were sick too?
Me: Then we'd call your Godpapa or Godmama
(N) What if they were all sick?
Me: Then we'd call our friends
(N) What if everyone was sick except the police?
Me: (after some thought) then the police would call Child Protective Services to make sure you had a safe place to stay while they tried to get your family on the phone.

I think the words Child Protective Services sounded comforting to him, and he was quiet. I remembered when I was a child wondering what it would be like to be all alone in the world, and knew he probably just wanted to know that it would still be okay for him to be a child. That there would always be an adult who could make sure he had a place to stay and food to eat.

I wonder if there is anything I could read him tonight that will lessen his angst, and make him feel secure in his life, or if all the transition and growing in his young life will inevitably well up into bedtime worries.