What I mean is:

"Both Willy [a wizard] and Harry are required to work out the exact nature of the main task of the contest which they both achieve in a bathroom assisted by clues from helpers, in order to discover how to rescue human hostages imprisoned by a community of half-human, half-animal fantasy creatures."

is very comparable to your completely hypothetical example above.

So, if a paragraph of cherry-picked, high-level description are the only identified similarities, there is no case in copyright law.