A scuba-diving vacation in Australia turns serious when Miss Mallard and Willard discover that the Great Barrier Reef is being destroyed. But how? Why? And by who? These questions lead them on a search, literally under the sea, where Dr. Decoy, bent on world domination, has built an incredible underwater city. Miss Mallard, Willard, and the undersea explorer Jacques Canard throw a wrench into Dr. Decoy's plans and save the reefs of the world.

A world science conference in Kenya is disrupted when two famous scientists go missing. The clues reveal the scientists have returned home, but Miss Mallard knows better. She smells a rat, or in this case, a duck with plans to take over the world. Miss Mallard has seen it all before and her clipping file confirms that Dr. Decoy has escaped from jail. Now all she and Willard have to do is prove he's in Kenya, catch him and save the world.