For several decades now, it's been accepted comic book lore that it was Neal Adams who ended the campy era of Batman thanks to his subversive redrawing of Bob Haney's Brave & Bold scripts so that day scenes became night scenes, and Batman became darker and moodier. All those great O'Neil & Adams issues of Batman and Detective had their roots in those B&B stories. Right? Isn't that how the conventional wisdom goes? The only writer other than O'Neil that gets any credit at all for reviving the classic 1939 Batman mood to the Silver Age comics is Frank Robbins.
And yet, here's the thing: Thanks to these SHOWCASE PRESENTS: BATMAN volumes, which I've been slowly working my way through, all the available evidence points to the least likely suspect as the one who brought back the Dark Knight: Gardner Fox himself, in Detective # 374, along with artist Gil Kane (and cover artist Irv Novick). The plot itself, "Hunt for a Robin-Killer!", is pretty slight (especially for Fox), but the main point of the story is obvious. After three opening pages of somebody brutally pummeling Robin to the point of near death, rendered in Kane's patented rolling thunder from panel to panel, Batman goes on a rampage of anger to track down Robin's attacker and bring him to justice.
Here's a panel description from page 4: "In the gloomy confines of the warehouse a frightful fear stirred in the hearts of the trapped trio! For they -- and evil-doers like them -- had generated the phantom of the night -- whose very shadow struck them like a thunderclap of doom..."
Another page 4 panel: "Nerves snapped before the attack of this nightmare nemesis of the Gotham City underworld!"
Page 6: "Woe to Robin's assailant! An enraged Batman has become a terrible figure of vengeance!"
Page 8: "I've never felt such hate for any human being! I'm caught up in a compulsive vendetta!"
Here's the clincher: Detective # 374 was cover-dated April 1968. Brave & Bold # 79, Adams' first stint on the title, was cover-dated Aug-Sept 1968. Frank Robbins' first Batman story was Batman # 204, cover-dated Aug. 1968 (drawn by Irv Novick). So you can give the credit to Fox, Kane, Robbins or Novick, but it looks to me like Adams & O'Neil just perfected the moody revamping of the Dark Knight, rather than originated it.