Granite, Narvarth and Danaëlle are trapped on the planet Glèbe. Fortunately, Federation ships have established a base there. It is imperative to join them. Cataleptic Narvarth and Danaëlle out of service, it is alone, with her two unconscious friends, that Granite must take a suspended train, the Imperator Express, where she is engaged as hostess. But she does not know that she is being monitored by an individual interested in the technological weapons she hides...