The protagonist of The BFG (Big Friendly Giant) is an orphan, a little girl named Sophie. The story starts as she is lying in bed, unable to sleep:
The moonbeam was brighter than ever on Sohpie's pillow. She decided to get out of bed and close the gap in the curtains.
She reached out for her glasses that lay on the chair beside her bed. They had steel rims and very thick lenses, and she could hardly see a thing without them.
(Dahl, The BFG, Amazon.com)
This allows her to accidentally see a giant, who normally remain hidden, and it is her good luck that he is the only friendly giant in Giant Country. Sophie learns about the other giants, who eat children, and along with the BFG she travels to the Queen of England for help in stopping the other giants. Sophie is precocious and smarter than other children her age, and after her initial fright is determined to keep the giants from eating any more children; her persistence allows the Queen and other heads-of-state to combat the giants and imprison them for murder.