From publisher blurb: An officer with the Ilsunsi Directorate Intelligence Services approaches the travelers to discuss a delicate mission. The Olonsean Empire has begun building "Planet Buster" bombs using a newly discovered radioactive element. This new element has only been discovered on one planet in the Sonora sector of space. All of these minerals are transported by a monorail from the mines to the local star port. He wants that monorail blown up. He also wants the travelers to seize the shipment and bring the minerals to him.