ANTIQUES ROADSHOW plants itself in Bismarck, North Dakota, and host Mark Walberg and appraiser Ken Farmer visit a farm where the main crop is farm-related collectibles. At the Bismarck Civic Center, appraisers harvest a wide variety of fascinating objects, including a Victorian convertible bathtub; a valuable Dakota language bible purchased for almost nothing; and a presentation script of the Academy Award-winning 1935 movie The Informer, signed by director John Ford and cast members, and valued at $4,000 to $5,000.