This is an essay about two late-twentieth-century French philosophers, Michel Foucault and Louis Althusser, and Marxism. My thesis, simply stated, is that Foucault and Althusser pursued the same basic theoretical trajectory in relation to Marxism and that this trajectory is both rooted in and leads decisively away from Marx and Marxism. I argue that Althusser was stymied in this trajectory by his adherence to the French Communist Party, leaving Foucault to fulfil it.