The Knight on the Grid - S3-E8
Other mistake: Towards the end of the episode, Bones and Booth visit social services and discover the identify of an elderly man whom they then suspect to be a Gormagon Master, who had retired from social services and lived in a nursing home. Much earlier in the episode, back at the lab, there is a glass panel with a flow chart of Masters and Apprentice Gormagon's - one labeled Master has the picture of the old man from the nursing home - this is before the visit to social services or the nursing home. (00:28:20)