The story begins on a small spaceship docking with a refueling station. On board are a group of four aliens, Bernard, Sandra, Desmond, and Julian. During a particularly tedious period of their stay at the station, the other three begin playing with the ship’s controls while Bernard is outside playing spaceball. They accidentally disconnect his part of the ship, leaving him stranded while they crash into a large blue planet close by (Earth).
The French government sends for Holmes when the Mona Lisa is stolen from the Louvre. Holmes swiftly decides he is dealing with a mastermind - and none other than his old enemy Professor Moriarty himself.Holmes foils Moriarty's plans to sell Leonardo da Vinci's masterpiece and trails him to Switzerland, where they meet and fight to the death above the famous waterfall at Reichenbach.