The cave is actually an entrance to a downed spacecraft whose inhabitants have succumbed to a virus, leaving them dead. Many of the ship's robots are still functioning, however, and the players must either avoid or defeat them; some may also be ignored. As later seen in video games, "plot coupons" need to be collected. The adventure requires the players to gather colored access cards (the "coupons") to advance to the next story arc: entering restricted areas, commanding robots, and other actions are all dependent on the cards. "Expedition to the Barrier Peaks" comes with a booklet of 63 numbered illustrations, depicting the various monsters, high tech devices, and situations encountered in the adventure. Much of the artwork for the adventure, including the cover, was produced by Erol Otus. Several of his contributions were printed in full color. Jeff Dee, Greg K. Fleming, David S. LaForce, Jim Roslof and David C. Sutherland III provided additional illustrations for the adventure.