After returning from a scouting mission in a time machine, the Mandroid gives a Roman centurion shield to his master Abbot Reeves. Reeves orders the Mandroid to be dismantled (killed), but Reeves' assistant Takada tries to help the Mandroid to escape. Although Takada dies in the escape attempt, he tells the Mandroid to seek scientist Col. Nora Hunter for help in stopping Reeves from enacting an evil plan. In the U.S., the Mandroid finds Hunter and reveals himself to her. She believed Reeves to be dead and recognizes her designs for a Mars probe in the Mandroid. She repairs damage done to the Mandroid in his escape. The Mandroid plans to return to stop Reeves' evil plans (whatever they may be) and Hunter insists on accompanying him as his mechanic. She also brings along S.P.O.T., a small flying scout robot of her own design.
Arriving in South America, Hunter hires the best river boat captain she can find in a seedy bar, one Harry Fontana, and they head down a river. After running afoul of rival riverboat captains and Reeves' men, they end up finding the Mandroid's crashed plane after an encounter with a tribe of cavemen brought to this time by Reeves' time travel experiments. They also meet Kuji, the ninja son of Doctor Takada, who has come to find his father. The Mandroid informs him that his father is dead, killed by Reeves. He joins the group, which then storms Reeves' headquarters, only to be captured by Reeves, now a cyborg himself, more advanced than the Mandroid, whose body is designed to look like Roman armor. Reeves plans to travel back to ancient Rome and become the new Caesar.
The Mandroid fights Reeves and is quickly defeated. Badly damaged, the Mandroid sacrifices his life to free the rest of the group. They pursue Reeves to his laboratory just in time to watch him escape to ancient Rome in his time machine. In frustration, Fontana smashes the laboratory control panel, causing the time machine to overshoot its target date and maroon Reeves hundreds of millions of years in the past.
Where was Reeves trying to escape in the time machine?
Ancient Rome