An epic romantic adventure based on the life of Billy the Kid, from his humble Irish roots and his early days as a cowboy and gunslinger in the American frontier, to his pivotal role in the Lincoln County War and beyond.

　　改编自Kristin Hannah的同名畅销小说，Katherine Heigl和Sarah Chalke主演。剧集讲述了两个好朋友三十年一路相伴走来的故事。　　原著小说还有第二本《再见，萤火虫小巷 Fly Away》。

《比利小子》讲述现实人物 - 法外之徒「比利小子/Henry McCarty」在美国当牛仔兼枪手，卷入林肯郡战争的故事。