case closed
Meaning
Expressing finality, that that preceding material is meant as final, not subject to amendation or variation.
Used other than figuratively or idiomatically: A case is closed; specifically, a police investigation or similar is resolved.
Source: en.wiktionary.orgExamples
I was a big Nancy Drew reader. Nancy figures it out. Case closed.
We will chase terrorists everywhere. If in an airport, then in the airport. So if we find them in the toilet, excuse me, we'll rub them out in the outhouse. And that's it, case closed.