After being humiliated (as he perceives it) by members of the Theatre Critics Guild at a coveted awards ceremony, Shakespearean actor Edward Kendal Sheridan Lionheart (Vincent Price) is seen committing suicide by diving into the Thames from a great height. Unbeknownst to the public, Lionheart survives and is rescued by a group of vagrants. Two years later, on Ides of March, Lionheart sets out to exact vengeance against the critics who failed to acclaim his genius, killing them one by one in a manner very similar to murder scenes from Shakespeare's plays.