Lieutenant Dean is an Enterprise-D officer who fences with Captain Picard and is with him when the first of the Manheim time distortions strikes the ship.
Dean appears in We'll Always Have Paris. In the opening scene he and Picard are finishing a fencing bout in the ship's gymnasium, which the captain wins with a neat touch.
As the two discuss the point, the moment repeats itself: both men find they have just lived the same few seconds twice. The effect is felt throughout the ship and across the sector, and proves to come from Doctor Paul Manheim's experiments with time on Vandor IV.
Dean has no further part in the story, but the scene is the first indication of Picard's interest in fencing, which returns in later episodes such as I, Borg.