A laboratory overgrown by thick jungle. A missing scientist. A secret formula. Carnival in Rio. Mysterious tribeducks. A pay phone. These clues lead Miss Mallard and Willard into the thick Amazon rainforest in the hope they will find a lost friend. When they successfully emerge, a secret plot to destroy the rainforest has been uncovered. But Miss Mallard has all the information she needs to reveal the villains true intentions and locate the missing formula that can save the rainforest once and for all.

Miss Mallard arrives in foggy London to visit her nephew, Willard, who is in town working on a big international spy ring case. Little do they both know that an innocent ride in a taxi and their kind attempts to return a lost birthday cake with its scripted birthday message to the mysterious Milly will lead Miss Mallard and Willard on a search through London that ends with them solving the very case Willard is working on.

Priceless artifacts have been stolen from all over Europe by an International theft ring. Following the clues, Willard and Inspector Bufflehead go undercover in Texas and stake out The Alamo. Miss Mallard travels to Texas to vacation with Willard after he solves the case, but when she is thrown from her horse, Miss Mallard stumbles upon a mystery of her own. It soon becomes clear to Miss Mallard that she and Willard are working on the same case, and thanks to both their sleuthing, the International theft ring is brought to justice.

A famous archeologist discovers an ancient Egyptian tomb while Miss Mallard and Willard are traveling on the Nile Express. After the archeologist loads the discovered artifacts on the train, one of the passengers goes missing. Miss Mallard's keen eye for observation, and Willard's knack for discovering clues soon find the missing tourist, and the clipping file in Miss Mallard's knitting bag solves a crime that no one even knows has been committed.

Miss Mallard organizes a costume charity ball at Neuduckstein Castle in Bavaria. Willard accompanies her to guard the donations, and it doesn’t take long for mystery to strike. It is said the ghost of a court jester haunts the castle and it looks like it’s responsible for the hauntings that plague the ball. Miss Mallard soon realizes there’s more than one ghost responsible for the hauntings, and she and Willard set out to prove who’s the real ghost of Neuduckstein Castle.

Captain Blueduck, the notorious pirate, and his legendary lost treasure set the stage for mystery on the island of Jolo in the Philippine Islands. Miss Mallard and Willard seek refuge from a storm in a great banyan tree and become embroiled in a case involving the ghost of Captain Blueduck. It does not take long for Miss Mallard to realize the ghost is a fake, but then who is trying to scare a poor family from their home and why? Miss Mallard and Willard learn the surprising truth: the villain is not trying to scare the family away but to force them to stay. And when Miss Mallard finds the lost treasure, that's just what the family gets to do.