"Night of the Reaper"
The story is self-contained and revolves around Batman tracking a murderer to a Halloween party. Not just any Halloween party, though, but one of Tom Fagan's legendary Halloween parties. Fagan was a huge comic book fan in the 1960s and 70s and held a costume party once a year that began with a parade through Rutland, VT and ended at his house where everyone in attendance dressed up as comic book characters. The party was attended by the biggest comic book fans of the period and a number of comic book professionals, including Roy Thomas, Marv Wolfman and Wendy Pini. In the comic, a great many guests are seen in costume: Superman, Batman and Captain Marvel, naturally, but also Spider-Man and Thor.
"The Screaming House"
Reprinted from Detective Comics #37