In my previous work, The Alternate History, I divided the alternate history genre up into four larger sections according to the nature of the larger narrative driving the text in question: eschatological (concerned with final destiny), genetic (concerned with origin, development or cause), entropic (concerned with randomness or disorder) and teleological (concerned with design or purpose) (2). I perceive written alternate histories as querying notions of history, including its nature, its purpose, and its outcome. My divisions – the nexus story, the true alternate history, and the existence of parallel worlds, where alternate histories lie side by side rather than being exclusive – focus on the moment of the break, not on the subject's position (5). The nexus story focuses on an important moment in history, the changed outcome of which profoundly alters what we consider established history. Some alternate histories posit the creation of a kind of temporal police, which ensures that history remains on its established, ‘true’ course, in order to bring about a particular, desired historical result. The true alternate history focuses on a world that appears to us to be greatly changed, the result of a change in a previous point in history – an England a few hundred years after the quelling of the Protestant Reformation, for example. Parallel worlds stories let all outcomes be equally likely and equally true: each changed moment in history branches into equally valid outcomes, where the changed event both did and did not take place.

In televisual texts, however, the larger notions of history queried by the literary form of the genre are not in play. Unlike written alternate history texts, they rely not on an historical analysis of history and its ultimate purpose but rather on an examination of individual characters and their reactions to the (from our point of view altered) world around them. This is done to address larger concerns of contingency and agency, the foregrounding of which indicates the presence of a contingency– agency feedback loop that ultimately serves to privilege the individual over the turning of the wheel of history.

Before I proceed, I want to define some terms important to what follows, which are mentioned in this book's Introduction: nexus event, contingency, and agency. A nexus event is a pivotal event that is crucial to history's unfolding as it has.