Good point. Upon further research you're definitely correct, a summary of a copyrighted work that uses none of the copyrighted work is still an infringement under US copyright law. If you're curious, in Harper & Row v. Nation Enterprises, 471 U.S. 539 (1985), the Supreme Court held that The Nation, the news magazine,…

And yet, when Pesel's father came to shave the other cheek, he was already gone.

This is what I came here to say. There is no copyright in facts, and a fact about a copyrighted work cannot be a derivative work, because the fact on its own is not sufficiently original. People can use copyright law to protect their livelihoods when the spoiler uses some of the copyrighted work, even only a tiny bit…

Well predicted!