Découvrir le pot aux roses
[day koo vreer leu po to roz
to uncover a secret
to discover the pot of roses
The idiomatic French expression découvrir le pot aux roses
means to find out something that was kept secret for some reason: trickery, shady business, misdeeds. The origin of this expression is unknown; theories range from love notes once being hidden in flowerpots to the secrets of making perfume.
dévoiler le pot aux roses
le poteau rose (literally, "the pink pillar")
C'était en écoutant leur discussion secrètement que j'ai découvert le pot aux roses.
It was by secretly listening in on their discussions that I found out the secret / uncovered the plot.