Any begonia people?
 

I don't know what kind of begonia this is, but I just got it a month ago. Hadn't been keeping up with watering, and as a result, some leaves dried up and fell off. And eventually one of the two stems turned black from the bottom and completely died, and then the other one started turning a darker green and getting wrinkly and kinda mushy. So apparently rot.

http://i.imgur.com/UJjKGhw.jpg

So I cut it, and the inside of the kinda-mushy parts is still light green? Usually rot has a discoloration.

I'll get pictures of it after being cut, whenever I find where the heck I put my camera.

They're hard to rescue when they're that far gone. Cut just below the bottom leaf. If the stem is still mushy or discolored there, keep going. Dip in a rooting gel or liquid (hydroponics shop.) Set in sterile medium that is just barely damp - it shouldn't even feel moist. Put in a jar or enclosure with 100% humidity and give it bright indirect light. Don't let the leaves touch the enclosure walls.