Batman is chasing down the Joker in Gotham, when the Joker appears to blow himself up. Some people might think the Joker is dead, but Batman knows better. The only question is what is the Joker up to? And given his past behavior, Batman honestly can't say.
The next day, Batman travels to meet the father of a friend of his, Ted Knight, a scientist, a man who just happens to be the father of Starman, better known as Jack Knight. Ted Knight is a master of science, while his son uses a kind of magic to fight crime, namely, the cosmic rod. He eschews the usual superhero trappings of a costume, wearing instead, jeans, a leather jacket with a star impression on the back and a plastic sheriff's Star badge from a Cracker Jack box. Ted and Bruce Wayne talk before he is about to give a lecture, but in the middle of the lecture, Yed Knight is suddenly kidnapped by Nazi Goons, who escape through a door that glows with a strange green light, and they have been wielding powers rather like green electricity.
That night, Batman answers the Bat-Signal to find not only Commissioner Gordon waiting for him, but Hellboy as well. Batman doesn't want Hellboy's help, but Hellboy says that the Nazi goons that kidnapped Ted Knight were out for him because of his knowledge of science. Science and magic are close, so often that one can be used to aid the other, and that if Batman wants to bring in the men who kidnapped Knight, he'si going to need someone who knows Magic... like Hellboy.
Together, Hellboy and the Dark Knight track Ted Knight's attackers through the city, finding a trail of men who have worked for them and prepared a special airplane for them to escape the city in. But when they get to the small airport where the men are waiting, the Nazi goons escape through a portal that nearly sucks Batman and Hellboy into oblivion and leaves behind a swastika-shaped symbol in the air. From the comments they made, they are heading for South America, and Batman and Hellboy are ready to give chase, only for a call to come from Gordon- Joker has reappeared, and he's threatening to kill children and turn them into twisted replicas of himself if he doesn't get what he wants. Batman must stay to bring him to justice, but someone else steps into Batman's shoes to fill in as Hellboy's partner- Starman, Jack Knight himself.
But what are the Nazis up to in the jungle, what are they trying to bring through, and can Starman and Hellboy take them out and wreck their schemes without killing Ted Knight along the way?
The second story crosses over Hellboy with the character known as Ghost. This female character was a detective who was killed, and she still isn't quite sure why. Tracked down by one of the B.P.R.D's Ghost Hunters, Hellboy attempts to put her soul to rest. But when a strange man claims that Hellboy can tell her something about why she was killed, if only she will capture him and being him to her, she does her best to do exactly that.
But the man spirit is lying to her, and when she finds out, can she free Hellboy in time for him to defuse the threat of the man and his hold over the lady? And can Hellboy help her find any closure on her life, and from her death? And can she and Hellboy lay the other ghosts to rest?
Both of these are stories published in limited edition series, crossed with another character or characters. The first, of course, being Batman and Starman, and the second being Ghost. It's a bit strange seeing Hellboy working with Batman, because neither of them usually inhabit the same universe: Hellboy is a character from Dark Horse Comics, and Batman and Starman are DC, but considering some of the other hero/villains that Batman has worked with in the past (Including Alan Scott, the magic-based Green Lantern whose weakness is wood, and Jason Blood, who is merged with the Demon Etrigan), it's not as farfetched as it might seem. And I suppose that given the weird things the average resident of Gotham has witnessed, seeing a literal demon walk the earth is just one more weirdness in a whole city of weird.
The Ghost crossover seems far more organic, if only because most readers of Hellboy will not know about Ghost or the universe she lives in, but when it comes to baggage, she has even more than Batman. She has a whole Louis Vuitton set. It's this that allow the ghosts and forces she is manipulated by to make her into such an easy tool. All they have to do is tell her that Hellboy might have had something to do with her death and she's all over attacking him over and over again, so it's up to Hellboy to save her from those who are lying to her and send the spirits to rest. And then her disillusionment is so extreme, she refuses to speak to him any more.
In both stories, the focus is more on the heroes that Hellboy is interacting with than Hellboy himself, but that's okay, as Hellboy, despite his complicated past, is really a simple character. He's a guy who has a job tracking down and dealing with evil things from other realities and making sure those realities don't invade our own. He might be a half-demon and also be Anung an Rama, the on who will bring the end of the world, but he's got a job to do and he does it. That's what he is, and it defines his character. Seeing him interacting with other heroes is nice, but in the end, not much changes. Hellboy does his job and goes on doing what he does- that's who he is as a character. But it's still nice seeing him puncturing the posturing of evil characters and spirits, because it's damn funny.
For those who love lots of Hellboy, I'd definitely say read this graphic novel. But it's not an essential part of Hellboy lore or something that you have to have in your collection. I'd say read it before buying it, and see if it's something you can't live without before forking over your hard-earned money to buy the stories. I won't be buying it myself because I already had the Ghost/Hellboy crossover, and the Batman one was only okay. Recommended to read, but not necessarily to buy.