Star Trek: The Next Generation - 4x21 - The Drumhead

    The Enterprise has discovered a spy, who transmitted sensitive data to the Romulans.  Shortly afterward, there is an explosion in engineering, which appears to be consistent with sabotage.  Picard has an Admiral on board who participates in running an investigation into the possible conspiracy.
    Whenever Starfleet Command gets involved, you know that things aren't going to turn out well.
    The actual conspiracy - the spy, the possibility of collaborators - is incidental.  The meat of the story is the Admiral running the investigation, and being willing to condemn people for unrelated offenses as part of a grander conspiracy.  The whole thing plays out as a McCarthy hearing, although Picard's way out of it is to quote the Admiral's father.
    For an episode that is moderately dark, it's pretty smart.