NOTE: if you haven't read The Long Halloween, do not continue reading this post, as it is just one long spoiler. The Long Halloween is mostly a murder mystery, and what I'm discussing here is its solution. It's also possibly the best Batman story ever written, and if you haven't read it and like Batman at all, I heartily enjoin you to go read it now.
One of the best parts of Jeph Loeb's scenario for The Long Halloween is its open ending, which leaves it to the reader to weigh the evidence and reach a conclusion. It leaves you thinking long after the last page about the story's central event: Harvey Dent's transformation into Two-Face. Specifically, it asks when Harvey Dent's corruption occurred. Was it at the moment of his greatest defeat, when a mobster ruined both his face and his life's work? Or was it earlier, when he began the work of ridding Gotham City of its gangsters as the serial killer Holiday?
My own belief is that Harvey Dent didn't become a murderer until he pulled the trigger on Carmine Falcone. The “two holiday killers” mentioned by Two Face at the story's end were Alberto Falcone, who publicly confessed to all the crimes, and Gilda Dent, who confesses to the reader alone that she committed the first three murders.
But Gilda herself has an alternate solution. She believes Harvey Dent picked up the killings on New Years Eve, when she left off.
Evidence Against Dent Being Holiday
The best evidence against Dent being Holiday is his own confession at story's end, when he reveals that there were “two holiday killers.” At that point, the only killer known to Batman is Alberto Falcone; there doesn't seem to be any point for Two-Face to make this statement if it isn't true, so I assume it is, at least from his point of view.
The only killing we witness is that of Maroni, the final victim, who is gunned down by Alberto Falcone. We can thus be certain that at some point, Alberto became one of the holiday killers. We can also be reasonably certain that Gilda committed the first three murders because she confesses them only privately, to herself (and us, the readers) – she has no ulterior motive for lying, and doesn't seem to be irrational or insane. Since she doesn't confess to any of the later murders, we can also conclude she did not commit any of them.
Evidence For Dent Being Holiday
The murders between New Years' Eve and Labor Day thus have two possible culprits: Falcone, and Dent. Gilda has two pieces of evidence to support Harvey's involvement: first, that when he came home on New Year's Day his hair was wet, although he supposedly came right from his office and was wearing his hat . Second, on labor day she found a .22 pistol, identical to those used in the murders right down to its filed-off serial number and taped handle, in his briefcase.
The first piece of evidence isn't very weighty; Harvey could have happened to put on his hat sometime after stepping outside. More importantly, it's not clear that a murder was even committed on New Years' Eve. The apparent victim of this holiday was Alberto Falcone himself, who faked his own death to go into hiding and begin his own killing spree. On the other hand, we are shown a body which washed up on the shore on January 6th. The fact that this body is never identified, and we are never told of anyone missing, leads me to conclude that this is just part of Alberto's ruse. He has acquired an appropriate body double (probably with the help of the city coroner), and this is the body which fools even his own father.
With no murder required on New Year's, the fact of Harvey's wet hair becomes meaningless. More damning is the .22 found in his briefcase on Labor Day. He claims, in a brief and strange exchange with Gilda, that the gun is 'evidence' he's holding for the trial – clearly, a false explanation. There are two possible explanations for this. First, it may be that Harvey Dent is preparing to begin his own holiday killings, using the serial killer's M. O. to mask his own campaign against the city's mobsters. I prefer the second explanation, however.
Dent has become aware at this point that Gilda committed some of the holiday murders; his statement at story's end that there were “two holiday killers” confirms this. He puts the .22 in his briefcase because he is prepared to “take the fall” for Gilda if the murders are connected to the Dent household.
The Balance of Evidence
Analysis aside, however, I prefer the Gilda-Alberto solution to The Long Halloween for emotional, not logical, reasons. If Harvey Dent was one of the Holiday killers, it undermines the drama of his transformation into Two-Face. If he was already killing gangsters at the time, then what's the big deal? The Long Halloween is about the fall of Harvey Dent, and I refuse to believe that fall had already happened one-third of the way through the book.
I admire the Hell out of Jeph Loeb for crafting such an ambiguous ending, though, and I respect anyone who reaches different conclusions about it than me. I favor my interpretation because my favorite part of the story is Dent's corruption. If your favorite part was how evil intrudes on the personal lives of good men and women, you might favor the solution Gilda sets out at the book's end. Or you might have an entirely different way of putting together the puzzle pieces. What amazes me so much is that one story can have several different plots, with different themes and ideas at their core – and that it ends by letting the reader decide between them.