Even Adonis was powerless when faced with an emperor who valued his integrity so highly. If no arrests were permitted, how could the investigation continue?
Anyone who plotted an assassination would first make sure to distance themselves from the act. If they were exposed, there would be no place for them in the entire world where they could hide.
Not to mention, not a single Jew was among the assassins, which to Adonis, was the biggest red flag.
Logically, as victims, the Jews should have been the most eager to target Napoleon IV; the emergence of a Dragon Slayer would have been a completely normal occurrence.
Unfortunately, without organized plotting, an assassination attempt wouldn't even come close to reaching Napoleon IV before the police caught them—and the Ministry of Police was not utterly useless.
As Adonis knew, since the anti-Semitic movement began, the police had continuously arrested over a thousand Jewish assassins and suspected assassins.