Like 'Pine Barrens' in "The Sopranos" and 'The Carousel' in "Mad Men," Rian Johnson's 'Fly' is considered a classic hour of television. Plagued by insomnia, due in part to his recent involvement in Jane's fatal overdose, Walter White is physically and mentally cracking. A common housefly buzzing around Fring's lab is enough of an irritant to force Walt to confront his tarnished morality. Like Banquo's ghost, it's a macabre reminder of what he has become and how much his life has spun out of control. As Walt finally tells Jesse when he concedes his pursuit of the fly, "it's all contaminated."