What makes a good whodunit? At the least, strong characters, clues and a clever twist. But also: interesting psychology, defective personalities or madness and multiple points of view, an ominous danger at large, and something that challenges justice itself, provoking us to speculate on wider societal issues or ills or the very human heart itself.
On my recent holiday I finally got to read Batman: The Long Halloween, which provides all of these. Best of all, it has a final chapter that keeps its secrets until the very last pages, as well as managing to subvert not only Bruce Wayne's mindset and mission as the Batman, but also perhaps the way we imagine our lives to be: secure and incorruptible and wholesome, while we set up structures and people as idols we will follow at all costs.
All of which ends up, I think, brilliantly, making the Batman into a valiant failure. How could he have let the murders keep happening, and why didn't he do more, sooner? Perhaps we should see it the other way: how could one man, limited by his own point of view and frustrated and distracted by his enemies, ever hope to redeem a city anyway? What does he have to lean on after all? The help of a few friends in Gotham? The hope of a better future? His brain, or being able to infiltrate and be there to stop crime at the right time? I think the way the ending comes about and the last words "I believe in Harvey Dent" mirror his own words "I believe in Gotham city" at the start show a world in crisis and a world where individuals act out of their own belief systems, at odds with each other. What a place of despair Gotham would really be - it's a bit like the repeated refrain of the book of Judges "everyone did as they saw fit" and great wickedness reigns because of it (17:6, 19:1, 21:25).
There's more going on here beneath the chaotic criminal goings-on and the beautifully dream-like noir-style of art (by Tim Sale, who drew art for and designed the look of TV series Heroes). This art adds to the whole by detailing the characters' expressions so we can believe in the characters feeling what they are doing - from the desperation of the crime-lords to the toughness of Jim Gordon. They only want to see things through...
For another good Batman story which acts as a whodunit, try Face the Face which is set much later, after Batman has been away from Gotham for a year. He comes back with perhaps a bit more humanity (which was cool to see) as he re-teams with Robin and tries again to work with Harvey Dent to uncover a murderer, but can he trust Harvey?