Distinguishing the comprehension of goal-directed actions from the enactment of those actions is the mental stage of planning, which we identify as planning knowledge. This distinction allows rehabilitation efforts to utilise reading comprehension of a fictional character's plans as a possible cognitive retraining tool. Hypothesising that comprehension of physical cause and effect is relatively intact in brain injury survivors, we compared survivors with high vs. low scores on the errand-planning task for comprehension of inferences based on physical cause and effect versus planning knowledge domains. Results indicate that those survivors with high errand-planning scores formed inferences from both knowledge domains, while survivors with low errand-planning scores were unable to form knowledge-based inferences. These findings suggest that a rehabilitation focus on comprehension of actions towards a goal state may retrain survivors’ skill at the mental stage of planning.