People
There is only one cure for grey hair. It was invented by a Frenchman. It is called the guillotine.
— P.G. Wodehouse ‧ The Old Reliable

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The setup sounds like a promise to solve a familiar concern about ageing, but the answer is grotesquely disproportionate. Naming the guillotine turns a supposed cure for grey hair into the removal of the person altogether. The calm phrasing makes the dark reversal especially abrupt.
Context reviewed