Detective Conan S01 E527 Evil Intent Hidden Behind a Mask

"One truth prevails."

Kogoro is invited by the manager of a theater to investigate strange occurrences. While Conan goes off to investigate on his own, he overhears Hiroshi Komazuka, one of the main actors, plan on switching a fake rapier with a real one to murder Robert Banno, another main actor, in the sword fight scene of the play