Seeking a return to normality after the Occupation, Jason orders Joseph to track down 20th-century television signals and gives Benny’s Time Ring to Peter, hoping to prompt the child to take them somewhere fun. Benny then walks in on them with Peter’s Grel godmother, Sophia, who is visiting the Collection, and Jason panics and orders Joseph to change channels. When Joseph does so, he picks up a time-shifted transmission from the planet Grellor, 45 years in the future, where a party of Grel are preparing to travel back to the year 2603, the present day, to kidnap the unique Peter Summerfield for study. Benny simultaneously panics and lashes out at Jason for trying to run off with her son, but as they argue, Peter picks up both Time Rings and puts them in his mouth. The Rings were only ever meant to be activated by Benny and Jason in tandem, but somehow, Peter activates both rings on his own, transporting himself, Benny, Jason, Joseph and Sophia to the Festival of Piranha, a deserted funfair in the year 2022.
Benny tries coaxing her son to take them back to the Collection, but Jason, irritated by her attitude, picks up Peter and takes him off to have fun at the fair. Benny follows him, but their argument is interrupted by the arrival of the Grel time machine. They try to flee in a nearby cart, but it turns out to be on a pre-programmed course for the ghost-train ride... and when Joseph accesses his data banks, he discovers that the Festival has been abandoned because a nest of flesh-eating Evatra Wraiths have made their home in the ghost train. As the Wraiths swoop in to attack, Benny tries to get Peter to activate the Time Rings again, but he’s having too much fun; only when Jason prompts him to think about the seaside does Peter transport them to safety. The pursuing Grel are attacked and devoured by the Wraiths, and the survivors resume their pursuit through Time.
The “seaside” to which Peter has taken them turns out to be the desert of ancient Egypt. Benny, fascinated, takes her son for a closer look at the Great Pyramid of Khufu, but as she shows the famous tomb to her son, a Grel digs its way up out of the sand in front of their eyes; the Grel time machine has materialised underground. Benny tries to flee, but the Grel shoots her and orders the furious Jason to hand over Peter. Meanwhile, Benny unexpectedly finds herself and her son inside the Great Pyramid, where they encounter Anubis, the god of the dead. Anubis declares that he is here to pass judgement on the life of Peter Summerfield; as the child has travelled through Time, his entire life is available for Anubis to consider, and to Benny’s horror, Anubis declares him unworthy to enter the kingdom of heaven. As the crocodile-headed devourer of the soul advances on them, Benny urges Peter to use the Time Rings to take them to safety...
Benny awakens to find that Peter has taken them to the jungle, presumably to see the wild animals. Benny tries to put her disturbing dream out of her head and convince Peter to take them home, but Joseph advises her to wait; the Time Rings were only meant to transport two specific people, but now they’ve been transporting an adult Grel, a child, and a robot porter along with them. When Benny tries to take the Time Rings away from Peter, she finds that they’re hot to the touch, yet they don’t seem to be harming her son. Sophia points out that Peter is unique, as the child of a Killoran and a legendary sorceress who was possessing the body of a human from another time period. This is why the other Grel wish to capture and study him. Benny scoffs when Jason tries to point out that he must be considered Peter’s father as well, and Jason, hurt, storms off into the jungle to calm down, taking Peter with him.
Meanwhile, the Grel have created a robot duplicate of Benny to infiltrate the group and take Peter, and once Jason is separated from the others, the Grel send their robot into action. The real Benny, unsure of whether she wants to apologise to Jason or not, tracks him down nevertheless, and catches up to him just as the robot stalks into the clearing and demands that Jason hand over the child. Benny loses her temper when Jason seems incapable of telling the difference between the real her and the version with the electronic voice and the wires sticking out of its back. The robot then refers to Jason as its husband, and when the furious Benny corrects it, the robot self-destructs, incapable of coping with the fact that it’s made an error. Jason assures Benny that he was just playing along to find out what the robot wanted, and Benny, irritated, refuses to discuss the implications of the robot’s apparent belief that she and Jason are due to remarry.
Peter next transports the time-travellers to a volcanic outcropping, where a group of Victorian schoolgirls are having a picnic. Within seconds, however, he’s taken them away again, and this time without saying a word to activate the Time Rings. The Grel arrive too late to catch the time travellers, but they do take the opportunity to test their newest invention: the Great Grel Gun, which reduces the unfortunate schoolgirls to atoms. Meanwhile, the time travellers find themselves making a number of rapid jumps, to a motorway, a soccer match, and the Eiffel Tower, where a bemused Frenchman mistakes them for Americans filming a Hollywood movie. Soon the travellers are jumping so quickly that they don’t even have time to work out where they’re supposed to be, and Sophia begins to fear that Peter has lost control of the Time Rings.
The time jumps finally stop, giving the travellers a chance to catch their breath -- but he seems preoccupied with something, and when Jason tries to pick him up, he finds that Peter’s entire body is now red hot. The Grel time machine then materialises nearby, and one of the Grel emerges and confronts the travellers -- but to his and Sophia’s mutual surprise, this turns out to be her son, Tim. Delighted to be reunited with his mother, Tim agrees to share information with the travellers instead of trying to take it by force. Unfortunately, before he can explain exactly why the Grel are so interested in Peter, his fellow Grel emerge from the time machine, presumably under the impression that something has gone wrong with the Gun and that Tim needs help to capture the child.
In the meantime, however, something very odd is happening to Peter -- and as the Grel surround him, he ages into a full-grown adult -- one with the strength of a Killoran male, but the mind of a child. Believing that the Time Rings are responsible, Benny tries to take them away from him, but he strikes her down, much to Jason’s fury. As the Grel swarm about Peter, Peter lashes out at them -- and as he doesn’t seem to know his own strength, each blow is fatal. Tim tries to shoot the Time Rings with the Great Grel Gun, but Peter attacks and kills him as well. The horrified Sophia picks up the Gun, but although Benny fears that she’s going to shoot Peter, she shoots the Time Rings instead. Once the Time Rings are destroyed, Peter reverts to a child again, and the shaken Benny picks up her screaming child to comfort him.
Afterwards, Jason apologises to Benny for calling her son a freak in his anger, but he can’t bring himself to believe that any son of Benny’s would ever grow up to hit his mother. Though shaken by what she’s seen, Benny vows to bring Peter up properly, prove Anubis’ judgement wrong, and ensure that the future she’s seen does not come to pass. Sophia examines the Grel time machine and finds that its circuits have been damaged by the constant, rapid time-hopping; however, the temporal circuits should survive long enough to take them back to their home time, if not the right sector of space. Benny decides to take the risk. As Jason prepares to launch the time machine, Benny tries to find some way to apologise to Sophia for her son’s death, but Sophia assures Benny that she holds neither Benny nor the young Peter responsible. She also admits that she’s been sending reports on Peter’s development back to Grellor, and thus may be responsible for their sending off the expedition in the first place. Jason then launches the time machine, and the travellers wait to see where they will end up...