To study Brennan is also to understand what it took to remain at the very top of a precarious profession for more than thirty years. Through Brennan and his pictures, we see Hollywood in the early stages of the sound era, its ascent to a golden age in the late 1930s and early 1940s, and then its decline owing to the advent of television--a technological innovation as formidable and threatening as sound had been to silent film in the late 1920s.