6. Great Uncle Oliver’s Code

On this adventure, the Kippernickker’s find themselves in a strange house identical to Sarah’s doll’s house. They are shown a mysterious code by Amanda, a girl Jonathan’s age, who is trying to solve the mystery left by her Great Uncle Oliver who hid in the house a fortune in diamonds. Amanda’s guardian, Miss Creaklestick (not all she seems) is also trying to find the diamonds but gets the code wrong. Matthew finds the diamonds and Miss Creaklestick escapes on her bike when Amanda’s real guardian appears.