This article argues for a more diverse approach to the appearance of enslaved persons in Greek historiography through an analysis of the Persian navy's battlefield tour of Thermopylae in Book 8 of Herodotus’ Histories. Previous approaches to slavery in Greek historiography have rightly commented on the cultural awkwardness to Greek authors of slaves’ extensive involvement in ancient warfare. However, this is only one aspect of how slaves featured in historiographical narrative. Herodotus continually problematizes the methods of enquiry and many characters within his work engage in enquiry-like activities. Book 8 itself is no different, with much of the action involving errors in human perception. The appearance of helots amongst the heroic dead at Thermopylae is intended both as a narrative reveal, since their presence has not previously been known to the reader, and as a comment on the contestation of Greek identity, which is framed at the start of Book 8 with a series of direct addresses to different groups of Greeks, all of whom take a different approach to their participation in the Persian Wars. Hence what appears to be an incidental detail can in fact be understood in the wider, thematic context of the Histories and especially that of the books concerning the Persian Wars.