Sophie's Grandfather Jacques Saunière brought her up, because her parents and little brother got killed in a car accident. Sophie did not know that her grandfather was not her Grandfather, but her protector and Grandmaster of the Priory of Sion. Once when Sophie came back home during spring break, she witnessed her Grandfather and other people she had never seen before participating in a Hieros Gamos (a 2000 year old sacred tradition). After that she ran away. She became a cryptographic investigator for the DCPJ (Direction Centrale de Police Judiciaire), her Grandfather would always make all kinds of puzzles when she was younger and she loved doing them. When Jacques Saunière died, he left a message after for Sophie:
13-3-2-21-1-1-8-5 O, Draconian devil! Oh, Lame saint! P.S. find Robert Langdon!
Robert and Sophie use this to find something, they had not expect...