Rain, who moved to the suburbs with Little Ken after escaping his own royal wedding, returns to Frog Kingdom after a series of explosions rock the capital. In the ensuing mass panic, with Frogizens fleeing the city, a chameleon distributes leaflets to the crowds proclaiming "Crystal Frog no longer protects Frog Kingdom! The end is nigh!" The Frog Princess, still furious with her runaway groom Rain, learns from her father that the Crystal Frog is indeed missing and that it can only be located by solving a four-line riddle.

Forbidding the Princess from leaving the palace, the Frog King has Bodie investigate, only for the ace detective to be ambushed and captured by the Big Four near the forest of cannibal plants. The King next sends Rain, Big Gua and the other Frog Warriors to rescue Bodie and solve the mystery of the Crystal Frog. The frogs encounter the Princess at the border who insists on joining them, intent on both saving her father's kingdom and keeping Rain in her sights. Together they form the impromptu Crystal Frog Protection Squad.

That night, while staying at a forest hotel, the Frog King's map of the kingdom is stolen from the Squad by fellow guest One-Eye. The Squad must locate One-Eye's lair, crossing the desert and entering the lair of the Ice Cave where solving the four riddles will not only prevent them from becoming frog-icicles but also secure the future of Frog Kingdom.