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.

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.