The strange man is Tony, Bianca's ex, who was carrying on a very manipulative affair with an underage Whitney. When it was discovered, everyone assumed it was him taking advantage of her and she was too scared to tell them the truth. Even when she did try to tell the truth, the adults thought she was just covering up because she was still scared of him. Since it happened, he's been locked up on remand.
Not sure whether Whitney's finally going to see the light before the trial is out, though.