When Oxley had been abducted from the Nazca sanatorium by Russian soldiers, Irina Spalko made him write the letter to Marion in order to trick her into travelling to Peru to investigate Oxley's strange actions. When Marion arrived, she was abducted, too. However, Spalko let her escape so that she could call her son Mutt Williams by phone and send him the letter with the order to show it to Professor Jones.
Mutt met Jones when he was about to leave the town and showed him the letter. After they succeeded to escape from two KGB agents who were behind them and the letter, they went to Jones' library in order to decypher the message.
The letter contained figures and text which Jones identified as being Koihoma, an extinct Latin American language with Pre-Columbian syllabic base. The text contained a riddle, reading:
- "Follow the lines in the earth only gods can read which lead to Orellana's cradle guarded by the living dead."
Solving the riddle
Jones correctly interpreted the "lines only gods can read" as the Nazca lines in Peru which can only be seen from above. However, he did not understand the reference to Orellana's cradle because Francisco de Orellana had been born in Spain. Only when he travelled with Mutt to Nazca and they found the map of the Chauchilla Cemetery on the floor of Oxleys cell in the Nazca sanatorium, he realized that the word used for "cradle" was a general word for "resting place" and that Oxley appearently had found Orellana's Tomb which had been unknown for centuries. Chauchilla Cemetery was guarded by warriors who wore terrifying skull masks, thus appearing as "living dead".