The Doctor was on his way to the library to see if he could find something in the books that might be of help with the current trouble in the TARDIS. He knew the odds were incredibly low that he'd find anything he didn't already know, but it made him feel better to be doing something. Something was horribly wrong, and he hated not knowing what to do about it.
He rounded the corner of one of the halls, expecting to be alone, and instead came face to face with ...
Himself. Only, the man in front of him was most definitely not a Time Lord. Not even part Time Lord.