Yet, the case rolls on, adding a Kafkaesque twist to the increasingly assertive actions of a security apparatus seemingly bent on proving the Kremlin’s harshest critics right when they say that Russia has taken a dangerous turn as President Vladimir V. Putin serves out what is supposed to be his final term.

The prosecution of Ms. Prokopyeva and other harmless critics comes against the backdrop of foreboding and uncertainty over what might follow Mr. Putin, who has anchored the system for nearly two decades. Even the question of whether he will depart as scheduled in 2024 is the subject of speculation, since he remains more popular than any opponent despite a dip in his ratings.

The resulting jitters, exacerbated by economic stagnation and mostly small but widespread protests that erupted this summer, have left Russia’s numerous law-enforcement bodies scrambling to prove their mettle against potential threats, no matter how puny, and secure their future in a country they all view as a fortress besieged by enemies at home and abroad.