Ever since Moominmama and Moominpapa (and Snorken) died when their flying machine crashed on the Snowy Mountains, Moomin and Snorkmaiden live together in Moomin House (with Little My) and struggle with the depression that comes with adulthood and orphanhood. Little My entertains them, but it lasts only for a while.
All of this changes with a sudden visit from Tofslan and Vifslan, and a Call to Adventure. Aside from the King Ruby and the Queen Emerald, there are other two Royal Gems: the Prince Topaz, kept in tunnels deep under ground by a misshapen moomintroll who was corrupted by the gem; and the Princess Sapphire, kept in a tower on the Snowy Mountains and watched by the dragon that Little My once kept as a pet. The Wizard wants to have all four Royal Gems to use them in a mysterious ritual.
Along with Snuffkin and the human boy Toft, a couple of gay amphibians, and a stuffed Tiger and kangaroo joey from the Hundred Acre Woods (Roo has become quite the emo goth), Moomin, Snorkmaiden, and Little My travel across the continent on a quest for the missing Royal Gems, as the Fellowship of the Gems. Along the way they visit the other realms of the continent: the Hundred Acre Woods, the Woods of Frog and Toad, the Land of Make-Believe, Teletubbyland, and Moominville (Muminköping), a walled town inhabited by fully-dressed, xenophobic moomintrolls. And also the Haven of the Prophet, the Wizard's wise seer ex-husband, who reveals that moomintrolls came originally from outer space... On the way, Snuffkin sacrifices himself to save the others from a perilous bridge (you shall not pass!) and returns resurrected and more powerful. And Toft and Roo fall in LOVE!
Moominvalley seems to be under the effect of a curse since that flying accident: the crops won't grow, the fish won't bite, the skies are ever overcast but it never rains. Bringing the missing Royal Gems to the Wizard, so that he unites all four Gems, will bring back the prosperity of yore... Or not?
Hemulen and Fillyfjonkan are now married empty-nesters. Ninni and Too-ticki still live together by the sea. Sniff has now got a girlfriend, Sniffmaiden. Kanga has remarried Rabbit, and Christopher Robin goes to university. The story is set a decade and a half into the future.
