this didn't go as originally planned

Mary-Lin's parents knew for a fact that Mary-Lin was in her bedroom, practicing the cello just like she had done every night after dinner for the past four years. There was absolutely no chance that she was, say, on a sinking row boat in Guam with her arch enemy, trying desperately to patch up a fountaining leak-caused-by-gunshot with one and a half tampons, a soy candle, and an expired can of dry shampoo.
Except that she was.

Hello and welcome to an interactive story in a new format, where together we will write this story into existence.