The year is 2046. Detective Ross Sylibus is transferred to Mars when a country singer on her flight is murdered. Making matters more complicated is that the singer is a "Third"—a robot that looks and feels like a human. Sylibus is partnered with Armitage—a beautiful female cop with a bad attitude. As they investigate the murder of the singer and other women on Mars, they uncover a conspiracy that can have them both killed by the Martian government.

A few years after they first met, Naomi Armitage and Ross Syllabus have started a family. Despite their normal lives, they must keep their identities a secret because many people believe that Robots do not deserve equal status with humans. Ross has an opportunity to abolish these ideas on Earth through a vote, but organizations in the shadows are working so that it doesn't happen.

In the year 2046 humans are moving away from using robots and begin to trust them less and less. In this time life becomes very perilous for the beings known as seconds. The seconds are the most recent line of robots, as far as the public knows. This is the world Detective Ross Sylibus lives in. Detective Sylibus is transferred to Mars by his request after his partner was killed by a robot. As he arrives he falls headfirst into a murder where a country singer on his flight was murdered. He steps off the plane and watches as a scene unfolds and he meets his partner, Armitage a female cop with a major attitude. A rash of murders begins when yet more women are killed. As the investigation is continued a secret is uncovered. There is another line of robots known as Thirds. More and more Thirds turn up missing, as a serial killer who is intent on wiping out all the Thirds runs rampant. Armitage in her quest to put the murderer to justice reveals a secret. She herself is a Third.

In the original storyline as aired in Japan, Dairugger XV was simply an exploration robot, as well as an intended peace-keeping force. The Earth is in a time of prosperity. The president of the Terran League (the "Galaxy Alliance" in Voltron) launches a mission to explore beyond the galaxy. After commencing its mission of exploration, the starship Rugger-Guard is attacked by a ship of the Galbeston Empire. Dairugger, the super robot, is deployed in order to defend the Earth. It is somewhat by fate that they must help the people of Galbeston find a new planet before it explodes, and liberate it from its despotic Emperor. In the Japanese version, it does not have anything to do with King of the Beasts GoLion, as opposed to the U.S. version, Voltron: Defender of the Universe. There are three assault team units: Land, Air, and Sea. There are a total of 15 parts referred to as "Rugger," which can combine together to form the super-robot Dairugger. The design of the 15 separate Rugger units came from the sport of rugby, since 15 players are required to form a rugby union. The U.S. version would rename the "Galbeston Empire" to "Drule Empire," along with editing a fair amount of violence and sexual content to keep the show safe for general audience broadcast.