ANTIQUES ROADSHOW, with host Mark L. Walberg, opens its lucky 13th season in Palm Springs, California, with a mix of great good fortune and an equally staggering loss. At one extreme, ROADSHOW experts discover the most valuable object ever appraised on the series: a 1937 painting by noted American abstract expressionist Clyfford Still - received as a housewarming gift - conservatively estimated to be worth $500,000. At the other, collector Jim McCarty invites ROADSHOW viewers to join the hunt for stolen works from his private collection of California plein air paintings.