just recently I entered Riften for the first time during the night and on the balcony of the Black Briar manor was a nightingale named 'Mysterious man." you couldn't talk to him or anything. upon finishing the quest Brynjolf gives you to steal Medessie's ring, the nightingale disappears.. I assume he might of been Mercer Frey? but I could be wrong. any suggestions on who he could be?