The affair on Langrenus now settled, Bob plans to return home. But an urgent cry for help from an old friend interrupts his homecoming. The Big Boss sends him a fleet of newly built fighter ships, seemingly just in time for this new and unexpected mission. Bob brings along a new ally, enlisting him in his growing little band of U-net agents. The new guy is James Jenkins, a.k.a Diamond Dog, a young, hot-shot pilot with smuggling connections and as soon as they set foot on Mars trouble blows up in their faces. A new city is being built and there will be a final gathering of the Allied Martian Powers. They've been planning their long-awaited and perilous mission - to destroy the loyalist alien military base on Europa. Bob and Diamond bring along much needed help to the cause, more than willing to rally to the side of the Alliance of Martian Powers but Bob finds that things are changing faster than he can keep up with and his experience in Langrenus haunts him in more ways than one. On Mars, alliances between humans and aliens are complex, tenuous things and Bob finds that even relationships with one's allies can be uneasy.