Has anyone tried this yet? I was in Uttering Hills Cave last night and found 3 prison cells that are opened and closed by chains on another wall. You think I could trap a follower in there or would they just fast travel home after waiting a few days?

And before you ask. No, I don't really know why I want to try this...

they might just go through it. Actually I think I got a follower trapped by accident like this and they returned home.

Marcurio once got trapped in a dungeon where the tunnels was blocked by stone slabs and he would have to move through walls to get out. Found him in Riften a few weeks later, as alive and snarky as ever.