Part 1: We start in the Frosticon lands. Krog, Chilbo and Snoof are just doing stuff when Snoof does something that gets him into a dangerous situation. Krog and Chilbo mix to save him, but they split in mid-air causing all three Frosticons to fall, making a crack in the ground that splits open an ice wall, revealing gears. Lots and lots of gears. The Frosticons get confused and go to find the source.
Part 2: Krog, Chilbo, and Snoof eventually find the source of the gears, which leads them to Klinker Land. Gox appears and introduces himself and the other Klinkers; the Frosticons freak and promptly Max. Gox pleads that he and his fellow Klinkers are friendly. Eventually, the Frosticons un-max, and some stuff happens.
Part 3: Jinky sees shadows in the distance. The Frosticons and Klinkers decide to Mix to go after the mysterious shadows, leading them to a rainforest. They un-mix and split up to explore. Gox and Krog find Spugg, Jinky and Chilbo find Turg, and Kamzo and Snoof find Tungster. The Lixers welcome them in. Nothing really major happens until the end, where it is revealed Major Nixel has been spying on them. He starts hearing footsteps and panics.
Yes, it ends on a cliffhanger. I think the Series 6 special might end with a fight against King Nixel. (well I was kinda right)