Down below is a place where everything burns, a world of ashes where the air can draw blood and the wind will cauterise the wound. The people who live here, assuming they are still people, burn as well - but it’s been a long time since they could feel it. Orders are given for the forge to be opened and the cradle raised. A ring is removed from the forge and handed to Tektekachuan. The ring was once dead, but he listens to it and says he can hear the voice of the Worm living inside it. He sends the ring to find its mistress, Bernice Summerfield, and orders it to bring her back to them as the Worm is waiting…

Up above, things are somewhat better, but this world has been broken for a long time so it’s hardly a paradise. At least in the sky the people that live here have a place where they can spread their wings and fill their lungs. The young reptile Ixotta is late by the time she joins Celethua, and the older creature was starting to get worried. Ixotta explains that she’d had problems with the air currents, but Celethua knows the forecasters had predicted another eruption today and what she really means is the air is more poisonous than usual. Ixotta has been asked to visit a new arrival in the colony, a creature that isn’t actually a pouchling, but is still the biggest mammal Celethua has ever seen. It told them its name is ’Summerfield’ and it doesn’t appear to be particularly unfriendly.

Celethua leads Ixotta down into the gallery tunnels where the ’Summerfield’ is being kept to stop it wandering off. It’s been a long time since Ixotta came down here so she has to readjust to the smell of the spinning mills. She asks where the creature came from and Celethua says it simply formed itself out of the air right in the middle of the colony. Everyone thought it was a ghosting at first, or perhaps a vision caused by one of the wild fields, but they soon discovered it was solid. Celethua tells Ixotta the creature had a piece of jewellery around its finger which it said allowed it to travel between here and the future. It claims to have come from a time 65 million years away, but Celethua thinks the creature must be confused. She assumes it’s just a language problem because every time the ’Summerfield’ uses a word she doesn’t understand she feels a prickling at the back of her head. Ixotta says this is a long way outside her jurisdiction and that Chulculum should really be here instead. Celethua asks how he is and Ixotta says he can barely move now. His wings had been torn off, but it’s not just what they did to his body she’s worried about, it’s what they did to his whole world. He hardly ever leaves the shrine now. They arrive at the gallery and Ixotta is surprised to see that the ’Summerfield’ doesn’t have as much fur as she’d been expecting. In fact its skin is soft to the touch, as if it had been bred in captivity. Celethua says they haven’t placed any guards over it as they don’t want it to feel threatened and in any case, she thinks it might turn out to be the best friend they’ve got.

Ixotta approaches the creature and introduces herself. The boy, Peter Summerfield, asks her if she’s a pterodactyl because she looks like one, even though she can talk. Bluntly, he tells her there aren’t any people like her where he comes from as they’re all dead. The reptiles tell him they’ve never seen anyone like him before either and he assumes that’s just because they have a very insular and mono-cultural society. As he speaks, both Ixotta and Celethua sense the prickling at the back of their heads again. Peter is angry at being spoken to like a child and says he’s very mature and has been trained in at least 16 different scientific disciplines. He explains that he comes from the 27th century, where they have rapid-eye teaching, but says even that is too slow for him. He says he came here using a Time Ring which just appeared one day right in front of him. He says his mother had one once, but she lost it. He assumes it’s the same one and that it came looking for him, but when he put it on it brought him here. He tells them he thinks he was drawn off course by a magnetic pulse and Celethua assumes he means the wild fields. Peter sensed that the force was alive somehow, like it was hungry and was trying to pull him towards its mouth. Ixotta is reminded of the Worm Callers.

Peter knows he’s come back in time millions of years, but he’s frustrated because they won’t let him go outside. He’s also been confused by Celethua’s attempts to feed him from her beak because he thought she was trying to kiss him, so now he will only accept food off the floor. He complains that it’s dark and smelly here and he’s fed up of being gawped at by pterodactyls. He tells them his ring has stopped working, as if something is blocking it, and he petulantly demands to go back to his own time. Ixotta tries to explain that although he’s not a prisoner, it’s dangerous outside, but Celethua decides that perhaps they might be able to help each other…

They take Peter back up through the tunnels and when they emerge onto the surface, the boy is amazed to discover they’re in the sky. The colony is a huge rock floating miles above the ground, but the reptile women warn Peter that their people don’t like to use the word “ground” casually. They’re so high up all Peter can see below them one big cloud. Celethua tells him it’s made up of smoke, ash and poison and Ixotta says it covers the whole world. Peter remembers learning about the asteroid that crashed into Earth and wiped out everything. Celethua says that happened a long time ago and the cloud has been there ever since, covering the ground and poisoning the air. She says their sister races still live down there on the land and in the sea and they’re still trying to farm their animals - the dinosaurs - on the surface, but her people never go down there as they can’t breathe the air for long.

The women are confused by Peter’s questions about what’s holding the colony up as they have no concept of gravity, but again they assume he’s referring to the wild fields. Celethua explains that when the world was cracked open, it released powers that had been trapped in the rocks since the beginning. The people used to live on the surface, but when the asteroid hit and the cloud settled they were forced to come up here. Peter has studied this subject and believes the collision must have released all sorts of psychic forces, but Celethua tells him that nothing that came out of the Earth was good.

Celethua takes Ixotta to one side and they discuss Peter’s claims that something pulled him here. They believe the Worm wants him as a sacrifice, or it might even be a personal vendetta. There’s a lot they don’t know about the Worm and they don’t even know why it attacks them. Celethua knows many of the reptile people are reluctant to discuss these things, but this ‘Summerfield’ creature appears to know things they don’t even have words for, so perhaps the Worm sees him as a threat. She thinks the boy may be their best hope for protection and might even turn out to be their saviour. Peter has heard some of what they said and he reminds them that the ring did actually seek him out, so maybe there’s a reason why he’s here. After all, his family does have a reputation for saving things.

The Worm calls to Tektekachuan and he realises the ring has returned and that the Worm can hear the voice trapped inside it. Not only has it come back, it’s brought the ’Summerfield’ with it. Tektekachuan realises it must be on one of the sky colonies on the other side of the cloud and knowing the Worm won’t be quiet until it has the ’Summerfield’, he sends his people out to find the creature…

Ixotta shows Peter an animal called a mulo, which her people use for carrying cargo. She’s guessed that Peter can’t fly himself, so she attaches a passenger harness to the beast for him to climb into. Peter wonders why they have harnesses at all if they can all fly, but she tells him not everyone can use their wings. Peter says he can feel something at the back of his skull and he realises Ixotta is talking to the mulo telepathically. She asks him not to talk about such things, but he tells her something must have changed in their brains when the world cracked open. That must be why they wear pendants around their heads, like a third eye. He’s sure he can fly the mulo himself, so Ixotta climbs aboard another creature and asks Peter to follow her.

They launch into the sky and Peter looks down on the broken Earth, taking in all the forests and the causeways and all the colonies that cling to the rock and breathe out clean air. Peter suspects Ixotta’s people take this sort of thing for granted, but he likens it to a chain of floating islands disappearing into the horizon. Ixotta is surprised to learn that where Peter comes from everyone lives on the ground and there’s no poison. Peter admits that in his time Earth is still polluted from all the machines, but Ixotta doesn’t understand his words and they cause her pain. He assures her they’ll go back to the ground one day. He admits that most people don’t have Time Rings, but his mother had one and she used it to go all the way back to the beginning of time once where she saved the Universe. But then his mother says that sort of thing a lot. Ixotta asks him if his mother knows he’s here, but he says that isn’t important. He says she only saves people because she makes trouble wherever she goes and then she has no choice. He insists that the Time Ring came to him, not to her.

Suddenly Ixotta screams at Peter to dive and the two of them bring their muloes down just as a poison stream passes above them. Ixotta says the streams can take people’s skin off if they meet them head on and she wonders if it means there’s a storm coming. She tells him to look down and he admires a beautiful lake below them, floating in the sky. She says this is the place where she was born, and it’s where her people farm fish. She points to a cave on the colony floor with carvings around the entrance and says it’s a shrine. Inside is someone who wants to meet Peter.

Later, Peter is uncomfortable because so many people are staring at him. Ixotta isn’t surprised as they’re wondering whether he’s an omen of the Worm or whether he’s come to protect them. And because he’s quite odd looking. Ixotta introduces him to the elderly Chulculum and Peter nervously says hello. The wizened creature replies, but Peter can’t understand him and he assumes it’s because Chulculum is so old that he’s literally speaking another language. Ixotta explains that he was born before the ground cracked open and Peter realises this means he doesn’t have the special ability in his brain. Chulculum speaks to Ixotta and says he was expecting Peter to come and that the Worm wants to avenge itself with the blood of the Summerfield family. Peter insists this has nothing to do with his family, but before they can argue further, they’re interrupted by the sound of the approaching storm. Ixotta says they’re under attack and asks for help in taking Chulculum to safety. She tells Peter to follow her to a gallery tunnel forty yards along the shore, but she warns him they need to get there before the Worm Callers arrive.

As they race outside the shrine, Peter looks up and sees creatures attacking from the skies above them. Ixotta urges him to keep moving, but they come under fire from burning lumps of rock and moments later the stone steps leading to ground level are completely destroyed. Peter points to another opening in the cave and although it‘s just a mulo shelter and doesn’t lead anywhere, it’s the only available cover. Once they’re safely in the tunnel, Peter asks who’s attacking them and Ixotta tells him they’re the Worm Callers. Peter says they look not dissimilar to Ixotta’s own people, but they seem “broken” somehow. Ixotta says the Worm pulled them out of shape and poisoned their blood. She refers to them as the Storm and says the forecasters usually know when they‘re coming because they make ripples in the wild fields. Peter realises she thinks of them as a force of nature, but he tells her they’re an army. As a student he once did a fast-track module on simulated battle tactics and military history and he wonders if he can apply any of it to their situation. Ixotta clearly doesn’t understand his references to strategies or battle plans and Peter says they’ve spent so long in the sky they regard everything as a form of weather, so they don‘t know how to fight. He sees things differently to them and he now knows what Celethua meant about him coming to save them.

He asks Ixotta if she can use her telepathy to talk to other people, and although she says she can send basic signals, she’s reluctant to call for help as it would just put others in danger. He asks her about the cave systems and she tells him there are about 200 of them around this side of the shore. He tells her to summon everyone she knows and bring them all together so they‘ll be closer to their animals.

Peter starts organising the muloes into a circle so the Worm Callers are surrounded. Ixotta doesn’t understand what he’s doing so he explains that the part of her brain that comprehends battles got shut off when they left the ground. Peter steers the animals towards the Worm Callers and tells Ixotta that their enemy might be more vicious, but they don’t have any tactics either. He’s using the muloes like weapons, but to control the creatures by telepathy, Ixotta’s people need to be within 20-30 yards of them. Peter warns them not to get any closer to the enemy than they have to, but Ixotta is having trouble sending the instruction as the Storm is getting worse. The prickling at the back of everyone’s head is starting to burn and it’s spreading out to affect the whole of their skin. Peter decides it’s time he spoke to the troops. Flying atop one of the muloes, he heads towards the Storm and rallies the animals together to close up the gap and stop their enemy escaping.

Tektekachuan and the Worm Callers have realised something is not right. They carry a rage so strong that it overwhelms them and although they’re on a mission for the Worm, their primal anger is such that they can’t remember what it is. Instead, they decide to tear their enemy to pieces, but somehow Tektekachuan knows at the back of his mind that he has to bring the ‘Summerfield’ back with them.

Ixotta warns Chulculum not to expose himself to danger. A lot of their animals have been killed, and although it looks like they’re starting to win the battle, a handful of their own people have died too and Chulculum wants to know why their forecasters didn’t see this coming. Peter returns and tells them the Worm is just another wild field, like gravity or a magnet, and it has nothing to do with blood. Suddenly one of the Worm Callers swoops down and attacks the mulo carrying Peter. Fortunately it doesn’t seem to be too badly wounded, but they realise the Worm Caller must have broken away from all the others and come straight for Peter. It’s obvious they’re learning about tactics…

Peter flies off and Ixotta realises he’s deliberately trying to draw the Worm Callers away. She catches up with him and warns him there aren’t any more colonies for miles in the direction he’s heading, but he’s determined to continue. He now realises the Worm Callers have been sent to find him personally and when they look back, they see their enemy has started to follow them. Unfortunately Peter’s mulo is wounded and they’re bound to catch up soon, so Peter announces that he’s going to head for the ground. Ixotta is horrified, but reluctantly she decides to accompany him.

Peter and Ixotta descend into the cloud but they can’t see anything through the dense smoke. Peter is sure he’ll be fine once he gets to the ground, but Ixotta reveals that the Worm Callers live inside the cloud and they know how to survive in this environment. She struggles to breathe and tells Peter she’s going to have to go back up. Just then, they spot a break in the cloud - but it reveals a glowing Worm colony. Ixotta has never been this far down before and she finds the sight horrifying. Peter realises the glowing is coming from a lake of molten lava. They decide to head off, but it’s too late and they’re soon surrounded. Tektekachuan arrives and insists they hand over the “seed of time”. Peter assumes the creature is referring to the Time Ring, so he rips it from his finger and holds it out, threatening to drop it into the lava below if they come any closer. Tektekachuan says it’s not the jewellery they want and the creatures swarm angrily towards Peter. He drops the ring in terror and calls out to Ixotta to fly away to safety. She hears Peter screaming, then he disappears from sight as she moves away into the cloud…

Back at the colony, Celethua is organising the retreat of the survivors from the attack. She arranges for any wounded reptiles to be taken down to the upper galleries and asks anyone with a dead animal to use its body to help block the tunnels. Ixotta arrives and learns that a full-scale evacuation is in progress. Celethua tells her they’re taking in refugees from a nearby colony where the air is practically on fire and the Storm is ripping the place open. Ixotta explains that the ’Summerfield’ has gone, then she says she needs to speak to Chulculum, but Celethua breaks the news that the Storm has taken him. Ixotta says the Storm is actually a battle, and for the first time, Celethua understands exactly what she means. Just then, the entire colony shakes and Celethua says the sky itself is turning against them…

Peter is dragged struggling down a tunnel. He warns the Worm Callers that he has a whole army to protect him and can make them attack whenever he wants. Tektekachuan introduces himself and when Peter tries to convince him he doesn’t have to do what the Worm says, he asks how they could they ignore the screaming of the Worm in pain. He orders the forge to be opened and proudly shows Peter the ’crucible of the ring’, but the boy says it’s just a pit full of lava. Then Peter starts to hear something and sees a shape swirling inside the lava. Tektekachuan says this is the voice of the Worm and says it will soon avenge itself on the ones who fly through time and carry the seed of time is their blood. He says the Worm found Peter’s broken ring and they put his voice into the metal and then sent it to fetch Peter from the future. As Tektekachuan orders the others to drag Peter to the edge of the pit, Peter realises they think he’s female. Tektekachuan suddenly stops and looks more carefully at Peter, then he announces that they need to send the ring into the future again. Unfortunately Peter explains that he lost the ring and Tektekachuan becomes uncontrollable enraged. He now realises Peter isn’t the one they wanted, but he orders the boy be lowered into the pit anyway in the hope that it might stop the Worm calling, at least for a while.

Suddenly the ground shakes and another Worm Caller tells Tektekachuan that burning rocks are dropping from the sky. Tektekachuan is baffled as he knows the sky colonies don’t have any artillery, but he quickly orders the forge to be closed to protect the Worm. During the distraction, Peter takes the opportunity to escape from his guards and flees into the tunnels.

Celethua realises their colony is about to split open, but there are still new refugees arriving all the time. She urges everyone to fly to safety, but Ixotta refuses to leave and says this was her home. Celethua can feel the prickling everywhere she turns and they realise it’s caused by something new - not the Storm or the battle, but something else, under the surface trying to make itself felt. To their horror, the entire west side of the farm breaks away from the colony causing water to spill out into the air. Celethua suggests they leave and get as far away as they can, but Ixotta refuses to go, convinced that whatever is breaking through is almost here. Then seconds later, the air itself seems to split open…

Alone in the tunnels of the Worm Caller colony, Peter stops and tries to work out what to do next. The ground continues to shake and rocks fall dangerously from the walls - and to his surprise, Peter sees there are metal pipes inside. He realises this must be how the forge works, but before he can investigate further Tektekachuan arrives. Peter warns him not to come any closer or says he will twist a control on one of the pipes. Tektekachuan blames him for what’s happening here and says that if he opens the pipes, he’ll release the voice of the Worm. He says the voice can tear into anything and even crack open time itself, but this only convinces Peter that he can blow the entire colony up if he chooses. Tektekachuan says he’ll destroy himself at the same time and Peter bravely accepts this as the price of saving the others. Peter twists the control and suddenly the entire tunnel seems to collapse in on itself. Peter finds himself hanging over a ledge over a huge drop. He begs Tektekachuan to help him, but he refuses and says the Worm can never be satisfied now. There’ll be no peace and no silence, just the howling for the rest of their lives. Peter is about to slip when one of the muloes flies straight into Tektekachuan’s back. The leader falls over the edge and disappears into the darkness below. Peter turns to the figure riding the mulo and, believing it to be Ixotta, thanks her for saving his life - but as the figure moves closer, he realises it’s his mother!

Tektekachuan survives the fall and is helped to his feet by some of the other Worm Callers. He’s badly wounded and needs support, but he tells the others what happened and sends them to collect the real ‘Summerfield’ who he recognised on the upper level.

Bernice tells Peter that she’s met his friends on the colony above the clouds and she rebukes him for making a mess of things. She points out that he’s started a fight they can’t hope to finish and when Peter tells her it’s because part of their brains have stopped working, she asks if it ever occurred to him that there might be a very good reason for that. She reveals that she used the Time Ring to come here. She knows he dropped it into the lava, but a little thing like a volcano isn’t going to do it any damage and in 65 million years time she’s going to dig it out again. After all, she’s an archaeologist and finding a buried artefact with a near unique isotope signature isn’t much of a challenge. She adds that the statues helped too, but she doesn’t have time to elaborate right now. She tells Peter it’s time they were going, but he insists on staying to help the others. She reasons with him and says that although he’s advanced in a lot of ways, he’s still just a child. He may think he’s an all-purpose Chosen One, but these people are in the middle of an extinction event and because they don’t understand what’s happening to their planet, they’ve placed the whole future of their society in the hands of a pre-pubescent boy. She tells him the planet is undergoing a massive change, like a rush of hormones, and everything is uncertain and vulnerable. It needs time to settle and grow up. She then reveals that the old man Chulculum died in the battle and says there’s only one thing that can help these people solve their problem. Just then, they hear the roar of several Worm Caller charging towards them, so they run for their lives…

Celethua and Ixotta watch in shock as the whole of their colony breaks up into pieces. They know it won’t be the last time they see this and that eventually the ground will take them all. Celethua suggests they head west, across the divide. The Storm seems to be spreading and taking the poison with it, but from down below they can see something else coming up through the cloud. Then Bernice joins them, obviously having been separated from her son. She tells them there’s been a slight change of plan as the Worm Callers are following close behind them, led by Tektekachuan…

Back in the tunnels, Peter is alone once again. He finds more pipes and starts to follow them, but when he hears a low moaning noise, he realises he’s getting closer to the Worm. He guesses this is the “voice” that the Worm Callers hear all the time. As there’s nowhere else he can go, he continues…

Ixotta spots the Worm Callers close behind them and says it’s just like when they were hunting Peter. Bernice admits that she may be a bit of a liability herself and suggests they leave her behind and go on alone. Celethua realises Bernice is the one the Storm wanted all along, but then she cries out in pain as the air stream starts to burn her lungs. The whole sky seems to be catching fire, but when they look down they can see even more shapes moving in the cloud. There are too many for them to be Worm Callers and Bernice thinks the Storm is twisting everything out of shape, the same way the Worm does. Everything that’s ever managed to get off the ground is being drawn up here. Ixotta is resigned to their fate and stops moving, but Bernice and Celethua urge her to continue and assure her the Storm is going to pass.

As the moaning in the tunnels gets louder, Peter calls out and asks the voice if it knows he’s here. He turns a corner and comes face-to-face with the Worm itself. It’s not what he expected, but Peter realises this isn’t the whole of the Worm, just a big lump of it. Tektekachuan had said earlier that the Worm always wants something, and Peter thinks he knows what he meant now. He thought the Worm would be like a huge brain controlling everything, but in fact it’s just a big mouth. The moaning becomes a howl and Peter knows what he has to do now. He moves a bit closer…

Celethua urges the others to gain as much height as they can, but there’s too much ash in the air and the she starts to falter. She says her wings are burning and her lungs are full of dust. She can taste the poison in her mouth and realises she’s too old for this. Below them, Ixotta calls out and says she’s found a rock that’s still stable where they can all rest…but it’s not long before they hear the baying of the Worm Callers close behind them.

Peter tells the Worm it might as well stop making that noise as he’s not going to give it anything, but the low inhuman moaning continues. Peter says everything started to go wrong from the moment the Worm thought it was going to get what it wanted. He realises he’s made things worse by coming here, but then he starts to feel the prickling sensation again in the back of his head. He says he doesn’t care why the Worm wanted his mother and he’s only interested in the stuff from the lava, the same stuff that the Worm is made of. Tektekachuan had said it could break open anything - even time! He touches it, but it burns…

When Celethua meets Tektekachuan she realises he’s the father of her first twenty offspring. Tektekachuan orders her to hand over the ‘Summerfield‘, but then Bernice steps forward and concedes that the Worm Callers have them at their mercy. She asks him whether he caught Peter, but when he tells her the Worm doesn’t want her son, she admits that she asked the question simply to distract him. Then she tells him she’s sorry…

Peter has realised the Worm isn’t actually the problem here, it’s just an extra annoyance and it only gets really dangerous when people listen to it. In fact, Peter himself has been the problem all along. It was only when he arrived that the Worm thought it was going to get its own way, and this caused the battle which messed up all the wild fields which led to everyone dying. He knows there’s only one thing that will help the situation now - he has to leave. The Worm starts to wail, but Peter says he’s going to walk into the lava and use its voice to crack open time, and there‘s nothing it can do to stop him. He’s already accustomed to travelling backwards and forwards in time and he’s proven he was able to steer himself away from the Worm’s influence when he was first brought here, so he‘s sure he can steer himself back too. He orders the Worm to be quiet, then he steps into the lava and asks to be taken home…