Answer
**Arrest.** Yezhov's meteoric rise within the NKVD came to an abrupt end in 1938 when he was arrested on charges of treason, espionage, and sabotage—the very accusations he had routinely leveled against countless others during the Great Purge. His downfall marked a significant turning point in Stalin's reign of terror, as the architect of the purges himself became a victim of the system he had helped create.