The Sparticle Mystery

When a group of children on a school visit to some caves return to the surface, every single person over 15 has disappeared. Opportunistic gangs roam the streets as Sadiq leads his newly-formed tribe to the safety of the City Hotel. After discovering her mum and sister missing, young scientist Kat takes charge of Liam, the boy next door. They too try to gain entry to the City Hotel, but only Liam gets in, leaving Kat to fend for herself.

Callum has formed a biker gang and has designs on the City Hotel as the gang's new hang out. He befriends Kat as she might be useful to his success. However, Kat is on her own mission to find out what has caused the disappearance of all the adults and encounters Reese at the City Library. Reese insists she can see the adults and feels she has found an ally in Kat. Meanwhile, inside the hotel, Holly is left wondering where her parents are.

Having won her place in Sadiq's gang, Kat leads a team to the University to find food. Holly is taken hostage by what appears to be the only surviving adult. Reese discovers a message from Doomsday Dora, explaining her heart theory - which also explains the curious survival of the adult who is actually - at heart - a child. The need to generate new sources of fresh food leads Sadiq to free animals from a city farm. This goes very badly until Tia discovers that the cheap perfume she wears is a magnet for the nanny goat.

After a year of searching for the Quantum Nexus, most of the tribe has split up. Jordan and Ami have gone to France, Kat is sorting out the nuclear power plants but everyone else reunites when they realize the key from Doomsday Dora fits into a stone head. But the head is in a stadium owned by Fizzy and there is also the matter that there is a traitor within their tribe. Reese is captured and the dims threaten to feed her to the lion if the Sparticles lose the fight. The lion is revealed to be a hoax and Holly is revealed to be the traitor, accepting a bag of Fizzys for doing a job for Fizzy. She vows to find the Quantum Nexus first and destroy it to determine the adults never return. She and Serena take off and the Sparticles take the Stone Head back to the Spartivan and set off on a race to the Quantum Nexus.

The Sparticles and Holly and Serena arrive at the museum where the stone head belongs and plan to decode the message on the Stone Head, but the Sparticles get caught up in a plan with another tribe, the Featherheads to raid the museum in order to get gold to melt down to turn into Fizzys to use to buy fuel.

The Sparticles and Holly and Serena bump into a circus tribe while searching for the white horse. For Serena, will it be a happy reunion with her sister?

It's been a year since the teen-aged parents were brought by Reece and the Quantum Nexis. The Sparticles are being held captive by Queen Kylie for ruining the lives of the kids from the 80s.

The Sparticles' mission to send Queen Kylie and the teen parents back to the dimension they came from hits a snag. Former Emperor Fizzy is after them.

The Sparticles find a third person with 'powers' like Reese, and the mission to rid the world of Queen Kylie moves up a step with the discovery of a curious map.