case closed
1. Said after a given question, debate, or mystery has been solved or answered. So you see, it was the dog who ate the blueberry pie, not me. Case closed!
2. The aforementioned decision, outcome, resolution, or situation is final, with no ambiguity or room for variation or amendment. The only way we'll be able to keep the company open is to undertake a 30% reduction in staff, case closed. My wife had an affair and our marriage is over. Case closed.