Xena and Xander Holmes, an American brother and sister spending a year in England, use clues in their ancestor Sherlock Holmes' casebook as they try to solve the mystery of a monster threatening a peaceful country village where a documentary film is being made.

Xena and Xander Holmes, an American brother and sister living in London for a year, discover that Sherlock Holmes was their great-great-great grandfather when they are inducted into the Society for the Preservation of Famous Detectives and given his unsolved casebook, from which they attempt to solve the case of a famous missing painting.

Xena and Xander Holmes, an American brother and sister living in London, use clues from their ancestor Sherlock Holmes' casebook to help classmate Alice Banders, who goes missing following the announcement that she will be crowned queen of Borogovia after her thirteenth birthday.