Title is mistranslated into English

"Secret Défense" does not mean "Secret Defense". "Secret" is the noun — the movie is about a secret — and "Défense" is the descriptive adjective. This is sometimes translated as "Top Secret", as though it were following a government classification scheme. "Défense" can mean a lot of different things in French; some words possibly better than "top", among those suggested by Google Translate, would be "protected", "interdicted", or "prohibited". Even though these mean very different things, any of them could apply to this secret.