This is the story of two women, Julara and Debrya. Both are ambitious, self-confident, and very determined to reach their goals. However, their lives couldn't be more different: Julara is on a spaceship headed for a remote planet called Acantarius. Debrya is a renowned linguist who has just joined a top secret project sponsored by the American government.

Julara must travel more than 42,000 years to reach the habitable exoplanet. Normally an impossible journey! Therefore she begins her voyage as a frozen embryo together with 5000 other human embryos which are also preserved in cryo-cooling units aboard the spaceship. Their task is to found a new colony on Acantarius. Once starship Perennial is close to its destination planet, Julara is unfrozen and her fetus is developed inside a complex machine called an Artificial Womb Device. Together with Sabelle, Ronyo, and Gilvan, she is the first human born on the spaceship.

The four children are nurtured and raised by two androids who teach them everything necessary to land the ship on the exoplanet and start their colony. The two human-like robots are the most sophisticated natural language processing systems ever built.

Debrya has the task to ensure the androids' programs are capable of handling the challenging mission. Not only do the lives of the four children depend on it; the survival of the entire human civilization is at stake as a gigantic supervolcano threatens to end life on Earth.

Before the starship is actually launched in the Year 2064, a secret experiment takes place in an underground facility, hidden somewhere in the Nevada desert. The experiment is to test the entire travel scenario. The first crew of the ship is unaware that their entire flight is a sophisticated simulation; they believe they are approaching and landing on planet Acantarius. Julara is part of that first crew. What she doesn't know is that her embryo was split before the artificial pregnancy, and only her twin sister will eventually make the real journey.

Debrya who has joined the project only recently is torn between guilt and the excitement of building the most perfect artificial life-forms ever. To her experimenting with the four children on the stationary ship seems highly unethical. But her fellow scientists convince her to stay on the project. Debrya's work is considered crucial. Repeated system failures of the androids in the experiment make it very clear the linguistic programs haven't reached maturity yet. As the apocalypse on Earth becomes imminent, the scientists are running out of time.

Twice in her life Julara is confronted with cruel deceit. On her sixteenth birthday she learns that her supposed parents are androids. Julara is shocked and distraught. The close friendship with Gilvan helps her cope. But after the landing, she is confronted with another appalling truth: she and her fellow crew are not on planet Acantarius at all. Instead they are on Earth amidst billions of other humans. After living their entire solitary youth inside a ship adjusting to the new environment is difficult.

The project team inside the facility desperately protect their secret. Therefore Julara and the others are not told what happened to them. At the same time, there are two more groups of identical twins alive in the United States and all are of different age. They are observed by the scientists to predict the medical and social conditions of the real starship crew when they grow older. Ronyo Greffin, an electrical engineer, is one of them. Everything changes when he learns he has an older twin brother. Eager to find out more, he hires a private investigator. With his help they uncover the secret project at last. Ronyo is overwhelmed to learn that he also has a younger twin who claims to have lived on a starship 42,000 years in the future and his starship is missing.

To keep the secret safe until after the launch of the ship in April 2064, the President of the United States reveals more details about the giant supervolcano with its potential to end life on Earth. He admits that there is no defense against it. Human civilization has to start over again on Acantarius, the nearest habitable planet with Earth-like conditions. As starship technology can't reach light-speeds, the embryonic cryotravel method is their best chance.

42,000 years later and 82 light-years away from Earth four babies are born on Perennial traveling in real space: Julara, Sabelle, Ronyo, and Gilvan. As predicted they are successfully raised by Debrya's improved androids for the first sixteen years. The future repeats itself as both genetic and environmental conditions are the same. But then the story takes a dramatic turn: while flying by a brown dwarf the androids malfunction and the four teenagers are on their own. They have to fight for survival on the starship. Nonetheless they reach Acantarius two years later as planned. The landing is difficult and a strange new world awaits them. But are they alone? They keep receiving an artificial radio signal from an unknown source. The puzzle is eventually solved when a second ship arrives at their landing site.