Well now I'm all mixed up because I thought this week was the season finale.
That said I hate when tv shows get aired out of order so I hope they air the one that was set to be shown yesterday before they show any further new episodes.
EDIT: Ok so I just found out this upcoming Friday December 21st was set to be the finale and still is. Apparently Thursday SyFy was set to show a marathon of all the episodes of season 3 so far. If things had gone according to plan the 12th episode "Reunion" would of been a repeat like all the others on that day. Due to the events of the last few days the "rerun" will actually be the first chance people will have to watch it. So to sum it up: the episode is airing the day before the season finale.