Harold Bell Wright 
The Mine with the Iron Door [EPUB ebook] 

The Mine with the Iron Door is novel of by American author Harold Bell Wright that was published in 1923.
Plot
As described in a review in a film magazine, Bob Hill and Thad Grave, two aged prospectors, find a little girl in the hut of a bandit Sonora Jack and take her away, but are unable to locate her parents. When Marta grows to woman-hood, Hugh Edwards appears on the scene and they fall in love with each other. Natachee, an educated Indian who hates the white race, learns that Edwards is an escaped convict who was convicted for embezzling funds. Edwards saves his life and in return Natachee shows him the location of the lost mine with the iron door, formerly worked by the Dominican priests and filled with gold. Just then Sonora Jack returns and, unable to find the mine, kidnaps Marta to hold her for ransom. Hugh and Natchee overtake him and kill him while rescuing Marta. Papers prove that Marta is the daughter of the man for whom Hugh was falsely sent to prison, and that he has since died confessing his guilt. Hugh and Marta finds happiness in their love for each other…|Wikipedia|