The Plot is an explanation of the The Protocols of the Elders of Zion. It traces their historical development, from an unrelated book published in 1848 [The Dialogue in Hell Between Machiavelli and Montesquieu], copied with slight renaming into the first “Protocols” by just changing the dialogue to a “report”, and mutant descendants from there.
It’s a thorough and largely scholarly look, told as a comic book. It works, particularly given Eisner’s strengths… but for me, it would have worked as well as a long prose pamphlet.