The kernel of the discovered attack for Black on the f-file should be evident enough. It also should be plain that this is a setup for a discovered check. Black can exploit the pattern by plotting a two-move course for his bishop. Look for White pieces that, like the bishop, are on dark squares. The queen always is a preferred target. Bd4+ attacks it, and BxQ takes it a move later after White moves his king out of check. (Or White moves his queen to f7 to block the check, and loses it there to Black's rook.)