This article examines the use of the kus ‘where’-interrogative clause in the second position of a question–answer adjacency pair in Estonian informal interaction. Applying an interactional linguistic approach, I will demonstrate how speakers use the kus-interrogative to point out the inappositeness of their interlocutor’s question. The use of the kus-interrogative in the second position implies that the questioner should already know the answer before asking. Essentially, the kus-interrogative is a response that negates the presumption posed by the polar question. Nonetheless, the negation is not sufficient to close this question–answer sequence. Instead, the interlocutors treat the kus-interrogative response as a challenge by subsequently justifying their question.