I`m looking for the title of a book. Its about a family of 4 (a father, mother and 2 sons) finding this spring in a forest and they drink from it then they become immortal. After some years go by they leave the town because they weren't aging and the towns people are noticing. Then years later they come back to the town. A little girl (I don't remember her name) sees them drinking out of a spring from afar so she asks if its good so she can drink it too (or something like that). but they didn't want anyone to know about the spring because they didn't want people to suffer like them and so they take her with them to try to explain to her that people can't know about the spring. After being with them for a night she trust them and decide not to tell anyone about the spring. Unfortunately her parents were too worried about her and called the towns serif and he or some guy in a yellow suit? wanted to find the spring and sell it to people so that he can make millions. currently that all i remember and that should be some what if not how the story is.