The International Astrophysics Commission under the direction of General Henderson is responsible for clearing near-Earth space of orbital debris. While Straker and Henderson clash over the priority of debris clean-up, a Moonbase shuttle is destroyed by an Alien device hidden in the debris, and Moonbase is cut-off from Earth. Straker orders the Interceptors to destroy possible hiding places in an 'end run' around Henderson, but the Aliens's plans involve more than a blockade, and so do Straker's.