WARNING: The following contains spoilers for "The Gift" in Detective Comics #1027, by Mariko Tamaki, Dan Mora, Tamra Bonvillain, and Tom Napolitano, on sale now.
Amid Detective Comics #1027's celebration for 1000 issues of the Dark Knight, Mariko Tamaki, and Dan Mora's "The Gift" sets up the series' next big mystery by reintroducing a famous item from Batman's deep lore through a "Joker War" tie-in story. The issue is set on the 3rd day of "Joker War", and starts with a two unassuming Gotham PD cops responding to an alarm at Wayne Enterprises that a masked Lucious Fox calls in.
However, unbeknownst to the cops, Batman is responsible for setting off the alarm. The two police officers rush into the scene to Batman's surprise and horror as the whole thing is revealed to be a set up when a Joker bomb explodes, engulfing the two officers. Batman acts quicky, pushing the non-engulfed officer out of the flames, before disappearing into the night. The surviving officer backtracks to his now dead friend and promises to get revenge, blaming Batman for the tragic event
Batman is next seen out of costume and presumably brooding upon his failures at Wayne Enterprises that resulted in the officer's death. However, in the next panel we see him holding a familiar item from his past, the Black Casebook, before tossing it the side on his bed amongst various Bat paraphernalia.
The Black Casebook is a record of Batman's earlier adventures in the '50s and '60s that featured otherwordly sci-fi, supernatural elements, and details on the Dark Knights secret projects. Stories involving the book were collected in Bill Finger, Dick Sprang, Lew Sayre Schwartz, and Sheldon Moldoff's graphic novel of the same name Batman: The Black Casebook. these stories would go on to inspire Grant Morrison, Tony S. Daniel, Sandu Florea, Alex Ross, Paul Dini, and Dustin Nguyen's "Batman R.I.P." storyline in the mid to late 2000s.
The Detective Comics #1027 anniversary issue is a fitting place for the return of the black casebook, seeing as it is a celebration of Batman's history. While the story sets up the series' next story arc with the murder of a Gotham PD officer being blamed on Batman, the presence of the Black Casebook signals a possible return to the more supernatural and science fiction elements of the Batman mythos that filled the detective's early years as a vigilante. How these two plot points intertwine in the future remains to be seen, likely to be answered in the future pages of Detective Comics.