"I'm not that easy, either."
Charles Sternhart was an English archaeologist and antique dealer. Sophia Hapgood summed him up as "English, good family, solid schooling. Fallen on hard times". Sternhart's schooling included a variety of languages, including German, Spanish, French, Italian, and Yiddish.
Biography
In 1939, Charles Sternhart was searching for additional artifacts from Atlantis, after the discoveries made by Jastro, along with Thorskald in Iceland, whom he was planning on contacting. Indiana Jones and Sophia Hapgood visited him in his shop. The trio entered a pyramid and discovered a tomb, not in the regular Mayan style. While Hapgood examined the tomb's glyphs, Sternhart stole an Atlantean piece from the tomb's skeleton and abandoned Jones and Hapgood.
Later, Jones and Hapgood encounted Sternhart again, inside the Labyrinth of the Minotaur on the island of Crete.
Behind the scenes
The Sternhart character differs significantly between the Fate of Atlantis comics and game. The above article mentions only the common parts of his character.
Sternhart according to the comic
Sternhart appears as tanned, short and stubby, not unlike a Mexican local. He managed an antique store in the Yucatan, Mexico.[1] The pair showed him Thorskald's discovery (a horned idol, and he led them on horseback to some ruins on unknown origin in the area. There they discovered a sarcophagus that contained a horned skeleton and a 'puzzle piece'. Soon after they fall into a booby trap. As Sternhart left the ruins, he also stole the pair's horses and presumably found his way to the Labyrinth of Crete.
Much later, Sternhart was being attacked by Nazi thugs in the Labyrinth when Jones intervened, preventing the Nazis from stealing Sternhart's piece of the puzzle. Sternhart, mortally wounded from a knife, was glad to see Indy, and told him of Hans Ubermann's treachery, and wished Indy success in beating Ubermann. He died, leaving Jones his moonstone and diary in which he had worked out the secrets of the location of Atlantis - off of the island of Thera. From his notes, Jones and Hapgood were able to reach the core of Atlantis before the Nazis, led by Ubermann and Klaus Kerner.
Sternhart according to the game
In the game Sternhart is a taller, thinner man with a fair complexion, and an Englishman; in the CD-rom version of the game, he speaks with an English accent. He is found in a Mayan temple at Tikal, who also held a small commercial stand with trinkets and souvenirs such as pewter replicas of the temple, mugs, 'genuine' floaty pens, postcards, 'official' key rings. Sternhart claimed to be the translator of the Lost Dialogue of Plato and allowed the pair to enter the temple only after Indy proved to him that Indy was not a tourist but a scholar, by knowing the actual name of the Dialogue: Hermocrates.
Inside the temple, Indy managed to open the tomb by repairing an elephant-head statue (to their surprise, since there are no elephants in South America). Sternhart steals the Worldstone found there and disappears behind a secret trap door. The pair are left behind only with an Orichalcum bead.
Sternhart is found again in the Labyrinth, but not shot by Kerner. They find his skeleton, having trapped himself there until starved to death. The Worldstone he stole earlier in the game is beside him for the player to take, his Sunstone and Moonstone are crushed by the player's elevator as it descends although the player has their own at that point. His notes lay also there but do not provide significant hints about the finding of Atlantis, as in the comic.