Medical History is full of stories of amazing detective work. Why not something like the discovery of Prions? You could talk about Kuru, Creutzfeld-Jakob disease,some of the others.
Or the story of the most famous surgeon in the US- Dr. Halstead at Johns Hopkins. He used cocaine (considered a mild stimulant at that time) and could work 20 hours a day. Of course he expected his Residents to be there too. As part of the personality change with cocaine use, he became compulsive about every bleeder being clamped and tied. This was the pre-antibiotic days, remember-- no pools of blood and fluid left behind, less of a culture medium for bacteria, so his infection rate dropped and survival rate went up. Now, anything that is shown to work in Medicine is quickly emulated. Thus began the terrible schedules Residents have to endure ( without benefit of stimulants) and a whole new system of surgery. Look at an instrument catalog-- Lots and Lots of Halstead clamps.
Or Watson and Crick and the mystery of DNA--
The discovery that DOPA actually got into the brain and changed the chemistry of the brain ( for Parkinson's disease)
The evolution of genetics and immunology - fewer and fewer "degenerative diseases" as we learn more about what is really going on. Very complex stuff.
Remember- if you can't dazzle them with your brilliance, baffle them with your bullshit.