The Lost Treasure of the Knights Templar III: The Mystery of the Snake Crown
The snake crown is stolen (or taken back) from the Knight Templars by the earth worshippers of Crete; the three kids try to retrieve it on behalf of the Knight Templars.
Includes: The Lost Treasure of the Knights Templar, The Lost Treasure of the Knights Templar III: The Mystery of the Snake Crown, The Lost Treasure of the Knights Templar II