This article explores the functions of paratextual and intra-textual pirate treasure maps in works of literature for children and young adults. Based on an examination of how the indexical X that "marks the spot" operates as the focal point of the semiotic endeavours of treasure maps, the article outlines the fragile stance of maps between referentiality (thus kindling readers' imagination) and the potential to disappoint reader expectations (since maps are never congruent with the territory they refer to). The discussion is exemplified by specific consideration of the treasure map from Robert Louis Stevenson's "Treasure Island" (1883) and the map of the turtle island in the German children's picturebook "Käpt'n Sharky und das Geheimnis der Schatzinsel" (2006), which are also seen as examples of treasure maps which play with the expectations of both readers and characters alike, all tied to the X found on any treasure map. The article ends with an analysis of the function of both maps and treasures in the context of open-ended reading games of imagination.