Description:

Where could Mr Goon’s nephew have disappeared to?

Mr Goon has forbidden the Five Find-Outers from solving mysteries – so they decide to make one up for his nephew, Ern! But what will happen when Ern disappears, and their pretend mystery turns into a real one?

https://books.google.com.pk/books/about/The_Mystery_of_the_Hidden_House.html?id=HSx_AAAACAAJ&redir_esc=y