Riddle of the Roller Coaster

Alex, David, Boris and Nikki are best friends. Under the influence of the courageous Alex, they go on all sorts of exciting adventures. One day, whilst exploring Aigamul theme park, they end up in the wonderful world of Lumagia - and what they discover there is too scare even for Alex!
In this magical underground kingdom, they encounter the formidably grumpy but lovely chef, Jammie O. He leads to his fantastical kitchen, where he is busy waging a battle against the vicious Sour Soldiers.
Alex and her friends soon vow to help him defeat them. If only they hadn't...