A method of conducting a wagering game on a gaming machine is disclosed. The wagering game includes a pay table defining awards and combinations of award symbols associated with the respective awards. After a player makes a wager, a plurality of symbol-bearing reels are rotated and stopped to place symbols on the reels in visual association with at least one active pay line. If the stopped reels include a combination of mystery symbols along the active pay line, one of the award symbols is randomly selected to replace the mystery symbols. The game provides an award associated with the combination of the selected award symbol, as defined by the pay table.