Literary term for the intro of a new plot line

[jayelmstreet]

Does anyone know if there is a term for this? What would you call the introduction of a problem into the plot of a story? It starts an arc that will need a resolution. It is like the introduction of a new thread. I am sure that there must be a term, but nothing comes to mind.

[dicer]

This is a bit late, but I don't really think there's a specific, literary sounding term for it. I would just call it a conflict and its resolution. This link might be helpful, though: http://bcs.bedfordstmartins.com/virtualit/fiction/elements.asp?e=1

[kelby_lake]

An obstacle, or maybe exposition if you're setting up a new arc.