There are many books from which I could pull from, but the best example would be The Hobbit by J.R.R Tolkien. Tolkien throws the reader into a mystical world set in Middle Earth. We are introduced to the main character, a Hobbit named Bilbo Baggins who enjoys a quaint, simple life in Bag End. Like many Hobbits, Bilbo Baggins does not like adventure, as it is not in a Hobbit's "nature." This changes when Gandalf, an old wizard, comes by to prove otherwise, to both Bilbo and the other Hobbits. During the novel, Bilbo is recruited by Gandalf to help a pack of Dwarves reclaim their lost home. When Bilbo accepts this quest, we begin to see Bilbo's true colors coming through. Bilbo scurries along to meet the rest of his party even as the entirety of Bag End shuns him. A great example of Bilbo's character in the dark is when he is literally in the dark. His quick thoughts are what saves him from being Gollum's next meal when he falls into his cave. Bilbo saved his own life that day because of his witty puzzles and quick actions against Gollum. On many other occasions, he is able to save his companions and continue their mission by using his wit and quick thinking. At heart, Bilbo is an adventurer, just like the Took side of his family. With the help of a couple of new friends, Bilbo was able to show his "true character in the dark" to the world.
I haven't added much, but I clarified some parts and revised a little. I hope this is helpful, good luck