Some time ago, Benny’s body was taken over by an ancient sorceress, Avril Fenman, who had an affair with the Killoran construction worker Adrian Wall. Benny eventually got her body back, and was later reunited with her ex-husband, Jason Kane -- only to discover soon afterwards that she was pregnant. Jason, torn by jealousy and self-loathing, has been picking up women in the local bars; Adrian is angry with Benny for not being the woman he fell in love with; and both men insist upon helping with the birth, in their own ways, whether Benny wants them to or not. Eventually, it becomes too much for her to handle, and she flees the Braxiatel Collection to give birth somewhere quiet and out of the way, accompanied only by her Pakhar friend and midwife Clair’atil -- Claire for short. But they lose control of their ship and end up in the Assimilated Territories, the area of space controlled by the Fifth Axis. Near the planet Dierbhile, they are shot down, arrested and charged with espionage -- and imprisoned in the infamous Glass Prison.

The Glass Prison isn’t actually made of glass, but it is entirely transparent (apart from the plumbing). New arrivals are processed and tortured on the first floor; the next three floors are reserved for female prisoners, and the remaining levels are for the men. Perhaps because of Benny’s pregnancy, she is not tortured when she arrives. She and Claire are imprisoned on D floor, where Benny finds that she has little to trade; the alien Terpsechians can generate euphoric drugs from their bodies, and other prisoners have their own skills which they trade via a system of credits and favours. For some reason, Benny is exempt from this system, which has been organised by the dominant prisoner, the Wolf -- for the Wolf is the leader of a cult which seems to have taken a strange interest in Benny and her baby. The guards are Aseks, who are either naturally asexual or have been genetically engineered that way; in any case, it’s impossible to bribe or corrupt them. It’s also impossible to pass between floors, which is just as well, because Kolonel Daglan Straklant, whom Benny and her friends once framed for treason against the Axis, is imprisoned on the floor directly above her...

Benny and Claire share a cell with Gripper, a former assassin for the Axis, and “Sophia”, a friendly Grel who has chosen to interact with other species using a name which means “wisdom”. Through Sophia, Benny finally learns the nature of the cult which has been annoying her since she arrived. Several centuries ago, a strange woman -- possibly a time traveller -- prophesied that in Deirbhile’s darkest hour, a saviour would strike down the planet’s enemies -- a “Child of Two Mothers”. This is why the cult has exempted Benny from the protection racket, and it seems that they also take credit for diverting her ship to Deirbhile in the first place. But after the birth, Benny will become irrelevant. And why is the Axis being so careful to ensure that Benny’s child survives unharmed?

Soon after Sophia’s arrival, a large number of cultists are arrested and brought to the Prison, and soon afterwards, the Wolf contacts Sophia to inquire about rumours of a new Axis offensive. Sophia, delighted by the opportunity to disseminate facts, reveals that several Alpha-class ships and the Imperator himself, have recently arrived on Deirbhile. It appears that the Fifth Axis is preparing to launch a massive offensive campaign, and the rest of the galaxy will never see it coming. And the Braxiatel Collection is right in the invading troops’ path... Benny doesn’t sleep well that night, and wakes the next morning to see that one of her neighbouring cellmates, Deedee, has been hanged. A threat has been scrawled on the wall in lipstick, and after the dinner hour, Benny returns to her cell to find a noose hanging over her own bunk. She later finds glass shards in her bed, and the next morning, Sophia accidentally spills some “water” from their cell’s jug on her prison-issue smock -- which completely disintegrates. Normally Benny’s the first one to splash water in her face on the morning, and it’s only by luck that she or her friends avoided permanent scarring. And Daglan Straklant has been watching it all.

Convinced that Straklant is responsible, Benny concludes that there must be a secret passage between floors; if they can find it, perhaps they can escape and warn the outside world about the forthcoming invasion plans. Gripper is shocked to learn that they know about this, and Benny realises from her reaction that she’s still working for the Axis, and was planted in the Prison to keep an eye on Benny. The Axis knew that the cult was arranging for the “Child of Two Mothers” to be brought to Deirbhile, and they surreptitiously assisted them in order to make sure that they got to Benny first. When Benny’s baby is born, the Axis will be able to present it to the cult and prove that it’s just an ordinary child, not a legendary saviour at all. As Benny ponders Gripper’s confession, the Aseks attempt to punish Sophia for losing her smock, and when Benny intervenes she’s sent to a cell on A block, where she nearly suffers from sunstroke. The Aseks return her to D block before she suffers any permanent damage, but the fear of nearly losing her baby has finally convinced her that the child is hers.

Once she has a chance to calm down, Benny concedes that Straklant can’t have left his floor, which means that one of Deedee’s cellmates must be working with him. Unfortunately, nobody saw anyone entering Benny’s cell to plant the acid. Thall, Deedee’s lover, seems stricken with grief, but could this be an act? Crow seems intense and psychotic, a much more likely suspect that the quiet and mousy Jevina -- but Benny isn’t really wililng to trust her instincts just now. She has no choice but to ask the Wolf for protection, but while she tries to be vague, Claire blurst out that they suspect Jevina -- and Sophia then claims that another prisoner has reported seeing Jevina planting the glass shards in Benny’s bunk. The Wolf promises to take care of the problem, and though Benny tries to protest that Jevina’s guilt hasn’t been proven, the cultists storm the cell and literally tear Jevina limb from limb. Benny is sickened, even more so when the Wolf admits that she doesn’t care whether Jevina was guilty or not; even if she was innocent, the real killer will now be too frightened to act again.

In order to get their minds off Jevina’s gruesome death, Benny and her friends discuss how to stop the Axis conference, and conclude that, since Gripper must be able to communicate with her superiors, they can use her to get messages out of the Prison. They thus ensure that Gripper can overhear them having “private” conversations, and try to make her believe that Straklant has offered to strike a deal with them for his freedom by revealing the identity of a traitor in the high echelons of the Fifth Axis. Apparently they succeed, for the next day Straklant’s cell is empty; he’s been taken to A block for intensive “interrogation”. As the day goes on, however, Benny finds that her belly is becoming much larger and more unwieldy, and eventually Claire must admit that this is going to be a problem. The baby has undergone a growth spurt in its last few hours in the womb, and it is already too large to pass through the birth canal.

Claire manages to convince the Aseks that Benny needs to undergo a C-section, and they send for a medical doctor to supervise the birth. On the day of the birth, however, the cultists turn on the Aseks en masse, throwing acid in their faces and seizing control of the block. The Wolf kills the Aseks one by one until finally one of them surrenders the control codes for the doors in the prison. This was done to ensure that the birth would go smoothly, without interference from the Axis, but it’s going to have the opposite effect if the doctor doesn’t get there. The Wolf sends Benny and her friends back to their cell, but shortly afterwards an alarm goes off and the entire prison is locked down. Someone must have used the wrong code; now, nobody can get in or out, not even Benny’s doctor, and soon Fifth Axis troops will storm the prison and kill all of the troublemakers. This is when Benny’s waters break and she begins to experience the first contractions of labour.

Sophia arrives with a man claiming to be Benny’s doctor; unfortunately, his assistant has been locked out of the prison, along with the equipment which the doctor requires to conduct the operation. With the doctor’s reluctant help, Sophia and the Wolf convince the Aseks to release the codes for A block, and thus gain access to Joseph, who can monitor Benny’s condition. They also acquire a number of confiscated weapons, including Sophia’s dataxe and a dagger with which the doctor can perform the operation on Benny. The Terpsechian, Zim, provides an anaesthetic from its own bodily excretions -- as it happens, the Terpsechians also generate acid from their bodies, which answers another of Benny’s questions. Benny thus survives the operation, and Joseph cauterises her wound afterwards. Benny awakens to see the doctor holding her son, just moments before Sophia kills the doctor with her dataxe. She’d noticed Gripper behaving oddly earlier, and when the cultists interrogated Gripper -- in such a way that she is not seen again -- Gripper revealed that the “doctor” was in fact the Imperator himself. It seems that the Imperator came here in person to investigate the reports about Straklant, and that when he was sealed inside the prison, he pretended to be Benny’s doctor. However, Sophia killed him before he could do what Gripper was always supposed to do herself -- kill Benny’s child, permanently depriving the cultists of their saviour.

Joseph reveals that he’s picked up transmissions from within the prison which indicate that Jason is inadvertently responsible for Benny’s problems, once again; he picked up the cultist Marianne in a bar near the Braxiatel Collection, and told her all about Benny and her child while drunk. Fighting has broken out in the prison, as many of the prisoners now have access to the weapons from A block and are taking the opportunity to settle old scores. Sophia and Joseph take the opportunity to slip out of the prison; when Sophia killed the Imperator with her dataxe, it absorbed all of the knowledge in his brain, including the override codes which she needs to open the exterior doors of the prison. Once free, she and Joseph send a message to Braxiatel, telling him of Benny’s predicament and warning him about the planned invasion. Unfortunately, they inadvertently release Straklant in the process, and he heads straight for Benny’s cell, along with Crow, his real ally on this floor. They never intended to kill Benny, just frighten her; Straklant wants her to watch him kill her son before she dies.

Benny’s stomach wound reopens from the strain, and she passes out before Straklant can kill her son. Straklant waits for Joseph to return, and forces him to seal the cell door and cauterise Benny’s wound. As soon as Benny awakens, Straklant prepares to kill her baby, but the child cries for the first time -- and Benny, lying helplessly on the floor, feels it vibrate. Benny orders Joseph to record and amplify the sound of her baby’s cries, and this shatters the cell door, enabling the cultists to enter and rescue her son. When Thall learns that Crow is the one who killed Deedee, Crow ceases to be a problem.

Reinforcements from the Fifth Axis then atack the prison, but to Benny’s disgust, the cultists allow the other prisoners to do all of the fighting while they hold a kangaroo court, trying Straklant for his attack on the baby. Thus, Straklant and the cultists are all gathered in the same place when Joseph realises, too late, that the echoes from his sonic attack are still resonating through the structure of the Glass Prison. The floor shatters beneath the cultists, dropping them all to their deaths. Benny and her son, Claire, Sophia and Thall are all on the edge of the room, and they thus flee to the stairs. Benny leaves Straklant behind, dangling over the precipice and unable to free himself from the cultists’ bonds, but she and her friends escape moments before the Glass Prison collapses behind them, crushing and killing all those who remain inside.