Bosola, in the ‘Duchess of Malfi,’ is of the same stamp.  He too has been a scholar.  He is sent to the galleys ‘for a notorious murder,’ and on his release he enters the service of two brothers, the Duke of Calabria and the Cardinal of Aragon, who place him as their intelligencer at the court of their sister.

     Bos.  It seems you would create me
     One of your familiars.

     Ferd.  Familiar! what’s that?

     Bos.  Why, a very quaint invisible devil in flesh,
     An intelligencer.

     Ferd.  Such a kind of thriving thing
      I would wish thee; and ere long thou may’st arrive
      At a higher place by it.

Lured by hope of preferment, Bosola undertakes the office of spy, tormentor, and at last of executioner.  For: 

    Discontent and want
  Is the best clay to mould a villain of.

But his true self, though subdued to be what he quaintly styles ’the devil’s quilted anvil,’ on which ’all sins are fashioned and the blows never heard,’ continually rebels against this destiny.  Compared with Flamineo, he is less unnaturally criminal.  His melancholy is more fantastic, his despair more noble.  Throughout the course of craft and cruelty on which he is goaded by a relentless taskmaster, his nature, hardened as it is, revolts.

At the end, when Bosola presents the body of the murdered Duchess to her brother, Webster has wrought a scene of tragic savagery that surpasses almost any other that the English stage can show.  The sight, of his dead sister maddens Ferdinand, who, feeling the eclipse of reason gradually absorb his faculties, turns round with frenzied hatred on the accomplice of his fratricide.  Bosola demands the price of guilt.  Ferdinand spurns him with the concentrated eloquence of despair and the extravagance of approaching insanity.  The murderer taunts his master coldly and laconically, like a man whose life is wrecked, who has waded through blood to his reward, and who at the last moment discovers the sacrifice of his conscience and masculine freedom to be fruitless.  Remorse, frustrated hopes, and thirst for vengeance convert Bosola from this hour forward into an instrument of retribution.  The Duke and his brother the Cardinal are both brought to bloody deaths by the hand which they had used to assassinate their sister.

It is fitting that something should be said about Webster’s conception of the Italian despot.  Brachiano and Ferdinand, the employers of Flamineo and Bosola, are tyrants such as Savonarola described, and as we read of in the chronicles of petty Southern cities.  Nothing is suffered to stand between their lust and its accomplishment.  They override the law by violence, or pervert its action to their own advantage: 

    The law to him
  Is like a foul black cobweb to a spider;
  He makes it his dwelling and a prison
  To entangle those shall feed him.