The Questers and Ranchers are reunited at Black Tor Mine where the adults were separated from the children by the machine of the Sparticle Project. But another tribe - the Mystic Moles - the children of the scientists working there, won't let anyone through the doors. Tia and Jeffery share a kiss. Callum arrives with the dictator and Kat kisses him as a thanks. The Sparticles face a series of challenges before they get to their greatest obstacle. Although they are successful reuniting the worlds, before the reunification stabilises, Kat stops the beam to save Reese's life. This disrupts the realignment process and the two world split again. Doomsday Dora tells the Questers to travel to the Quantum Nexus (hinting a second series). Just before Kat's dad disappears, he gives her a code to shut down the world's nuclear power plants.

• Jon East, Jonathan Fox Bassett, Tim Whitby

• Annette Badland
• Larissa Wilson
• Jerome Holder