The Sparticle Mystery

A trail is laid for the Treasure Hunt, but the two competing teams start falling apart. Loyalties become strained and old rivals become new friends. Holly understood the last letter of the last episode and is teamed up with Serena. Holly soon discovers that Serena is on the Sparticles' side rather than hers. Holly leaves her hurt by the riverside (Serena was hurt after a cut from the sword) and teams up with Ernesto and Fizzy and is soon joined by Reese to destroy the Quantum Nexus.They now make a group called The Freedom 4. The Sparticles soon find Serena using the tennis balls to guide them and discover the others are already ahead in the Quantum Nexus. Jeffrey stays behind to help Serena while the others go ahead and discover the Quantum Nexus.

A tribe of Traders lock up the Sparticles and accuse them of stealing their shipment which was to be given to Fizzy. They soon discover that the shipment was chocolate and that Fizzy is going to make an army using these. Serena and Holly are then captured and put into a room as the Traders thought they were Sparticles. After an escape planned by Frankie, Liam and Reese, they tried to rescue the others but were unfortunately captured again but Frankie and Liam escaped and found the balaclava and shipment and they discover that it's Skinny as he was 'sick' of taking orders from his boss. He is then arrested by Callum for breaking one of the rules but soon freed to help the Sparticles. Rocky stayed behind to help the Sparticles rather than Callum. Fizzy turns up and the chocolate is melted and Rocky tells to stay off the Quantum Nexus and the Sparticles to get chocolate and biscuits and it was agreed except of Fizzy who was frustrated.

The Sparticles travel to an abandoned mill where a supposed creature has been eating children. There, Tia and Jeffrey's relationship comes under strain and Rocky shows his true colors as he snatches the necklace Tia gave to Jeffery and throws it in the River blaming Jeffery for the incident. The Sparticles get their next clue, which leads them closer to the Quantum Nexus.

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?

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.

Ami lapses into a diabetic coma and the Questers rush him to hospital to find some insulin. Switching a generator on in the hospital may just have cost one baby his life. The kids running the hospital need fuel to run the generators to keep the babies alive. Aware of the ticking clock to get to the Project but desperate to put things right, the Questers undertake a dangerous mission as a solution. They have to distract a German shepherd dog who is guarding a yard full of petrol lorries. Meanwhile, it is Tia's fifteenth birthday. Will she be transported to join the adults in a parallel dimension?

The Ranchers have invited a tribe of seriously idle girls into their hotel. As they take advantage, the Ranchers are forced to fight back - but who will be turfed out of their home? Holly is anxious when she realises the journey to the Sparticle Project is coming to its conclusion. She leaves her fellow Questers trapped in an underground nuclear bunker, but there is another force at work. A computer who thinks there has been a nuclear war competes against the ingenuity of the children in a battle of wits.

The Questers are intrigued by Head Boy Jeremy and his posh boarding school. However, they are soon locked out and Jordan has left the tribe to become a true public school believer. Camped outside the school, ex-pupils Ernesto and his rebel gang recruit the Sparticles to overthrow Jeremy's regime and rescue the Unsuitables - the 'less-than-perfects' who do the dirty work for Jeremy and his cadets. The Ranchers at the City Hotel work out how to bypass the first door at the Sparticle Project. Working with Anita at the university, they come up with an ingenious solution, but now they need to get the key to the Questers out on the road.

A postcode given to Reese via Psychic Sarah at the fairground leads the Questers to a simulator where scientists were trained how to run the Sparticle Project. Ami, Jordan and Holly get trapped in the room with the prototype collider's super-cooling systems running, and the temperature is plummeting towards absolute zero. At the City Hotel, a fox has been at the chickens and the children decide to trap it. This is very tricky, but when they finally track down the animal and are set to destroy it, they decide on a better course of action.

Doomsday Dora's message has warned the children they must reunite the two parallel worlds quickly or adults and children will remain separated permanently. The ticking clock has started. The children decide to choose who goes on the road to the Sparticle Project and who stays behind to look after Liam and Frankie by an 'Apprentice'-style challenge to source power for the City Hotel.

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.