Look, a heating duct between the studs. I guess it should have been expected. But I was surprised.
We have a master plan which includes totally re-modeling the upstairs bathroom. Before we can do that, we have to add a shower to the downstairs bathroom, so that we have someplace to clean up while the upstairs bath is in transition. We had decided we could tuck a small shower under the staircase, and so we ripped into the wall, only to find a heating duct for the bathroom upstairs. Hmm. What to do? Stick with plan A or move on to Plan B. Move the duct or move the shower? We're waiting for a heating and plumbing professional to come and tell us what our options might be. Either way, it's going to be more complicated than we had originally planned.