The episode opened with an armed robbery that took place on the 555 when it took a stop on the Medical Treatment Asteroid (in Episode 67). Next, the 999 received an emergency stop signal and the Conductor halted the train in mid-space. Maetel was summoned by the C62 (the locomotive for the 999), who informed her that it was going to disconnect and go on its own. News of both incidents reached the Galaxy Railways Headquarters, and one of the operatives determined that both trains were on the asteroid when the heist occurred. The Conductor later discovered that the two robbers were on board the 999, and soon after the SDF appeared. One of the robbers took Tetsuro hostage and demanded that the SDF be attached to the 999. (thetvdb.com)