Paula Worth was searching not only for a rigorous question, capable of engendering genuine debate, but also for an engaging and enjoyable activity that would secure GCSE students' substantive knowledge. The answer--or rather the question--lay in counterfactual thinking: a carefully crafted game that she devised, based on the structure of a game by Jordan and Wood. Worth's game traced the events and decisions that led eventually to the collapse of Tsarist Russia. In this article Worth explains how the pursuit of "restrained" rather than "exuberant" counterfactuality allowed her students to analyse the consequences, and thus weigh up the relative significance, of different contributory causes. (Contains 5 figures.)