Sir Seth and Sir Ollie are back for their third adventure. Finding themselves high in the wintery mountains trying to stop a plague of avalanches, the two meet the elf queen Elynor of Ah Ah Kaachu, who tells them that Betty the Yeti is causing them. When they hunt down Betty, she informs them that the fault lies really with the Hole Thing, a giant blue caterpillar, which is located even further up the mountain. Ollie needs to get to New Kaachu to warn people of the next avalanche, and the fastest way there is to go through the Mids, which is the Snow Fleas' secret tunnels, but also where the evil Ghu lives. Seth continues up the mountain with Elynor to fight the Hole Thing, which is blocking a tunnel and causing the avalanches, while Ollie fights the Ghu. Can the two accomplish their missions and save the twon of New Kaachu from being buried by another avalanche, and also clear Betty the Yeti's name?
The prose in this is very lyrical and descriptive, and there is also a fair amount of action and adventure in struggling through their environments and fighting the monsters.