Not super sure.<br/><br/>I think I would probably go the route of having things go sour when the MC post comes in - if possible, let the original roller's post stand, and have the narrative flow go something like: "things were going [as per contents of original roller's post], but then [interference happening], and it all went to heck. Then [MC moves here]." Specific situations might need some editing, but that is how I would go for it.