To my simple mind, this puzzle was straightforward enough at the end, which made a nice change, and it was quite elegant in its simplicity.
The whole column and half a row to be highlighted do consist of two thematic names, or at least the names of precisely two people. They are situated symmetrically in the grid and together with the 7 letter person form a pretty good approximation to two half flags, I think.
I would maybe have used the word "found" instead of "hidden" in the preamble.
As for the title, I think it just refers to 31st October, which of course is central to the theme, and may or may not have lots of added significance for us all this year...
Great puzzle, even though like others I inwardly groaned at the theme :-)