Then I went to bed.
Then I heard bumpbump bump.
I jumped out of bed and intercepted him halfway out the deck door. He had it open and was stepping outside. I asked him what he was doing.
Dandy: I have to give them the thing.
Me: What thing?
Dandy: The thing. They said I have to give it to them.
Me: I'll take care of it. Your important part is to stay inside at night. It's not safe to go outside.
Dandy: They have to get the thing.
Me: I'll do it for you. Your part is to stay in your room. That's what you can do.
A few minutes later I went up to check him. He was in bed, eyes wide open, still sound asleep. "You have to close your eyes now honey. It's the next thing you have to do." His eyes close. "Stay in bed now. Dream of lovely things. Stay in bed."
We then booby-trapped the upstairs hallway so that none could pass without making a racket. I'm considering setting up a motion detector hooked up to a recording of me saying, "Go back to bed honey". He is very compliant and obedient while sleepwalking. It's just a matter of getting him to obey us, and not the dream.