Adventure of a Lifetime

This adventurous story is about a girl who's mother dies when the young girl is only 6. But, the girl, though young, knows that her mother did not die in a car accident as she was told. She died risking her life for something. So, at the age of 10, the girl and her brother, who's 12, set out on an adventure to find out wht their mother would risk her life for. But, the question remains.

Did her mother really lose her life?