Doctor: After having administered the curative, I'm confident the patient will recover.
Big Bro: Pfft, you're naive. The curative will kill us all, so while you weren't looking I mixed sulfuric acid into the concoction.
Doctor: But that will kill the patient!
Big Bro: No, his death is proof that your solution didn't work. If I hadn't taken action, the consequences would have been much worse.
Doctor: How do you know?
Big Bro: Well... err...
Doctor: Die in a fire.