By the time Paul marries Flavia, he is beyond all caring:
“The change was great, but Paul was no longer surprised at anything. He did not feel the faintest tinge of remorse; he only feared one thing, and that was that by some blunder he might compromise his future ... (The Mystery of Champdoce, Chapter 34)
In the end, Paul’s weak character and overall uselessness in the endeavours of life turn against Mascarin. Like a tool used against its maker, Paul’s very nature becomes Mascarin’s greatest punishment. This is a fitting and deliciously ironic end to Gaboriau’s excellent sensation novel.