One of the most unorthodox crossovers to date, DC's Dark Knight meets Mike Mignola's Hellboy! Ted Knight comes to Gotham City to lecture at a conference on alternative energies sponsored by Wayne Industries. But when Knight is kidnapped by a group of magic-wielding Nazis called the Knights of October, Hellboy offers his aid to Batman to help find Ted and thwart the Knights of October in their plans to marshal the Golden Age Starman's knowledge for their own nefarious purposes. As the heroes track the kidnappers--and their victim--to the Amazon jungle, they'll need some additional help: from Ted Knight's son Jack, Starman.
Golden Age Starman, Ted Night, is lecturing at an alternative energy conference and comes under attack by powered up Neo-Nazi's. The conference is associated with Wayne Industries and Batman is on hand, but he's unable to keep the Nazi's from kidnapping Ted Knight.
Hellboy contact Batman via Jim Gordon. The description of the Neo-Nazi's matches that of a group B.P.R.D. has been investigating. Hellboy thinks that working together may be useful in finding Ted Knight and stopping whatever the Neo-Nazi's have planned.
They track the group to an abandoned airfield outside Gothamand charge in to rescue Ted Knight. The Nazi's have numbers enough to slow them down and spirit Ted Knight off to South America. Batman and Hellboy are unable to follow right away due to a catastrophic contingency the Neo-Nazi's have in place. They travel back to Gotham to prepare to fly down to South America.
A situation involving the Joker requiring Batman's attention prevents him from getting on the plane but the arrival of Starman, concerned for his father's welfare, ensures that Hellboy will not be facing the Neo-Nazi's on his own.