Benny is supervising two first-year archaeology students, Emile Mars-Smith and Tameka Vito, on a field trip to the Chelonian digs on Apollox 4, when Jason Kane shows up, claiming to be in trouble and carrying a figurine of a young woman which he believes is the key to an ancient weapon of enormous power. Benny dismisses his claims as ludicrous but still spends the night with him. The next morning, he is kidnapped from his hotel room, and before she can report his disappearance she is arrested by galactic security troopers who believe that Jason passed encrypted data on his arms smuggling operation on to her. The artefact, however, contains no encrypted data, and they are forced to return it to Benny and release her. They refuse to investigate Jason's disappearance, believing that he's fled of his own accord; all their best information indicates that Jason and his female accomplice were searching for an ancient weapon with powers beyond that of a sun.
Benny, convinced that Jason is really in trouble, looks at the artefact from an archaeological perspective and determines that it comes from the prohibited world Ursu. She hires a pilot to take Tameka and Emile back to Dellah, but stops off in Ursu's system on the way for a quick scan -- only to be attacked by unmarked black ships. Their own ship is shot down and they are forced to evacuate, but the pilot, Errol, is seriously injured. They land near a quiet village, where they are rescued by a charming young man named Scott but face hostility from the other villagers, who fear that their presence will attract the "Sunless". Ursulans were once free to do just as they pleased, having set up their society here to get away from the profiteering of the corporations, but since the Sunless invaded a year ago senseless restrictions have been placed on travel and behaviour, and half of the population has been killed for violating the Sunless' codes. Furthermore, the Sunless have stolen the Blooms, the genetic pods from which the population of Ursu is grown in families of Eight; without the Blooms Ursulan society is doomed.
Realizing that the Sunless are closing in on the village and that Errol needs medical attention to survive, Scott agrees to take his visitors to the nearest city, where they seek shelter with his brother Michael. Due to a discrepancy in their birth -- their Family was bloomed with ten instead of eight, and some genetic data overlapped between them -- Michael was born with wings, but he has clipped them in order to fit in with the others of the planet. Michael is furious with Scott for bringing alien profiteers to the city, risking the wrath of the Sunless. Benny learns that hospital attention is now permitted only for those doing "essential" work, and Scott is horrified when Benny suggests kidnapping a doctor -- a suggestion which betrays everything Ursu stands for. Emile helps Benny and Tameka to kidnap Jock, a doctor from the local hospital, but Jock refuses to do anything for Errol while he's being held against his will. Benny, forced to make a choice, tells him to go, and once he accepts that she's set him free to make his own decision, he agrees to help Errol. However, Benny later learns that the Sunless have killed people for leaving their post before; Jock was as good as dead the moment she removed him from the hospital. Meanwhile, Emile, who is only fifteen and ran away from the University to get away from the strict rules of his father's religion, finds himself attracted to Scott; he hasn't admitted to himself that he's gay, however, and can't accept why he feels so upset when Scott and Tameka begin sleeping together.
Benny sees a group of angry Ursulans trying to attack a band of collaborators, and recognizes one of the collaborators as Jason's accomplice from the photographs the police showed her earlier. She, Tameka and Emile disguise themselves as entertainers and infiltrate a party for the New Administration, and Benny manages to get the woman Iranda alone. Iranda recognizes Benny and explains that she and Jason were acting as negotiators for the non-diplomatic Sunless; the Sunless' world was looted by corporations shortly before the galactic war, and they have been trying to reclaim the artefacts stolen from their world ever since. Jason fled with the figurine when he realized that the Sunless were trying to reassemble an ancient weapon. Iranda, however, claims to feel no guilt about her decision to collaborate; before the Sunless came, Ursulans were free to give up any job they didn't like doing any more, and the society was about to collapse of its own accord as vital jobs were going unfinished. Iranda turns Benny, Tameka and Emile over to the Sunless, but they manage to escape, steal a Sunless patrol car and drive it to safety.
When they get back to Michael's apartment, they find that the Sunless have been there; Jock and Errol are dead, and Scott and Michael are missing. Benny takes Tameka and Emile to shelter in what used to be the local university, vowing to get them home safely, and while there she uses the computers to translate the inscriptions on the female figurine. The inscriptions seem to claim that the visionaries will give themselves up to release power beyond the sun. Michael finds them and claims that Scott is being held captive in the spaceport, but when he leads them to the Sunless ship, they discover too late that he's collaborating and has turned them all in. Iranda is waiting for them, and she threatens to expel Tameka and Emile into space if Benny doesn't hand over the figurine, the "visionary". Benny has no choice but to do so, but Iranda is about to expel them anyway until Michael stops her. Furious, Iranda locks him up with the others, where he defends his choice to betray them -- at least fourteen other people in his building, frightened that their presence would bring the Sunless down on them, had already done so, and by turning them in himself, Michael hoped to convince Iranda -- his and Scott's sister -- to set Scott free.
The prisoners are taken to the Sunless' homeworld, a barren land barely heated by a swollen red star; forced to scratch out a harsh existence in the wilderness, the Sunless train themselves to be emotionless and ruthless from birth. Benny and her friends are thrown into a pit and forgotten, but the Sunless, who have dismissed them as a threat, fail to realize that Benny and her friends can work together. They climb out of the pit by standing on each other's shoulders, and in another, nearby pit, they find Jason and Scott, both of whom have been beaten half to death. Benny still doesn't believe that an ancient civilisation would just leave a powerful weapon lying around in case its descendents were ever in trouble, but Scott and Michael reveal that every one of their family has a recurring dream of falling into a glowing red light and releasing a devastating burst of energy. They use Tameka's makeup to disguise themselves as the pale Sunless and follow Iranda to the location of the "weapon", but they are discovered, and Scott and Jason are recaptured.
Benny and Michael, fleeing, meet Dr Kitzinger, an Ursulan midwife who was kidnapped when the Blooms were removed from Ursu; the Blooms were in fact a part of the weapon before the corporations stole them, and all the time the Ursulans thought they were building a free society with no restrictive family ties, it was based upon the looting of the Sunless' homeworld. Iranda's brother Nikolas, another collaborator, has been forcing Kitzinger to work against her will, and over the past year Kitzinger has been reduced from a free woman to a cowed servant. Nevertheless, she still had enough will to run away with the male figurine once she realized she was working on a weapon of mass destruction. Iranda threatens to kill Jason, and Benny has no choice but to surrender herself and the male figurine. Nikolas and Iranda place the two figurines in the places prepared for them, believing that the visionaries will give up their power -- but instead two grave-like openings appear in the crystalline base of the weapon. Benny, who has guessed the truth, reveals that the figurines were only representatives of the true visionaries -- Nikolas and Iranda themselves, who were generated by the Blooms to serve as part of the weapon. Their villainous behaviour has been a sham to cover up the fact that they've been acting as the result of biological imperatives.
Nikolas accepts his fate and steps into the grave, and Benny pushes the protesting Iranda into her own. Their absorption activates the machine, and just as Benny had suspected, it's not a weapon at all -- the inscriptions were mistranslated. Instead of releasing power beyond the sun, it powers the sun beyond its natural life. Light and heat return to the Sunless' world when the star is restored to youth, and while the Sunless remain unsure how to react to this development, Benny and her friends escape in Iranda's ship. Now that the Sunless' world has been restored to them, the Sunless will easily be driven from Ursu, and without the Blooms the Ursulans will be forced to rejoin the galactic society they'd shunned. Tameka discovers that she's pregnant, and Emile admits that he's gay. Jason and Benny are not reconciled, but Benny has come to a deeper understanding of who she is; she may be capable of cruelty and cowardice, but though surrounded by violence she endeavours to remain a woman of peace.
Source: Cameron Dixon