I've seen the use of interrogative pronouns in ordinary statements, not just questions. For example, from the book "Harry Potter y la piedra filosofal":
"Los Dursley se estremecían al pensar qué dirían los vecinos si los Potter apareciesen por la acera".
Rather than qué (what?), I would expect to see que - without the accent (that/which/who/what). Why is the word qué chosen instead? Is it something to do with the presence of the subjunctive verb that makes it different or special?
Thanks for any insights in this, for me, a very strange construction.