"The Case of the Chemical Syndicate", the first story that Batman appeared in back in 1939, was largely based on a "Partners of Peril", a Shadow pulp written by Theodore Tinsley in 1936. Though Batman's adventures would go to on eclipse the Shadow's fame, the Shadow's ethos has shaped Batman's identity, and a new Batman/Shadow series alludes to the nocturnal avenger genealogy.
The Shadow and Batman have crossed paths in DC's books in the past, and the younger hero has acknowledged that the Shadow played a crucial role in helping Bruce Wayne develop his alter ego. In the current Batman/The Shadow crossover series — from writers Steve Orlando, Scott Snyder and artist Riley Rossmo — Batman's origins are reimagined in a novel way that give the character's past encounters with the Shadow a new depth and significance.
Like all good, classic detective dramas, Batman/The Shadow opens with a murder — a murder committed by an unknown figure in the shadows that identifies itself as "an honest signal". Soon after Batman shows up at the crime scene, he's shocked to discover the Shadow, who is supposed to be dead, lurking in the darkness of the apartment appearing as if he was the murderer.
The two masked vigilantes briefly fight in the small confines of the room before bursting through a window and taking to the rooftop where they square off. Though they start off evenly matched, the Shadow catches Batman off guard when he reveals that he knows the contents of the letter from Bruce Wayne's grandfather that Batman destroyed as a teenager.
In this telling, the Shadow's classic ability to "cloud" people's minds manifests itself as ethereal laughter that floods a person's head, disorienting them and making them susceptible to the Shadow's manipulation. Though the Shadow escapes Batman, Bruce Wayne is unnerved at the idea that a hero he once respected might be back from the dead and on a murder spree.
When Bruce runs an analysis on the Shadow's face in the Batcave, he's identified as Lamont Cranston, a decades-dead ancestor of a murder victim with the same name. Unable to logic his way through how Cranston might have been able to come back, he seeks out advice from Henri Ducard, "The World's Greatest Manhunter", who once trained a younger Bruce Wayne in the French Alps.
Henri's more than willing to listen to Bruce describe his harrowing adventures of hunting a dead man through the streets of Gotham. But when his protege demonstrates he can't wrap his mind around resurrection despite all of the supernatural adventures he's had, Henri rattles Bruce's world by revealing that he is the Shadow. And Lamont Cranston. And many other people.
Batman's fervent disbelief in any of the mystical backstory that the Shadow tries to explain to him is one of Batman/The Shadow's overarching themes and one that uses Batman's classic distaste for magic as a basis to complicate his future. The Shadow tells Batman that in reality, he's a long-lived being who's assumed hundreds of different identities over the ages in his pursuit to eradicate the darkest kind of evil in the world. The Shadow here is a force of nature whose powers and purpose are matched only by a being called the Stag who seeks to kill the best people in the world — people who truly make the lives of others better. It's the Stag, the Shadow insists, who murdered the man that brought him face to face with Batman. But as we all know, Batman hates magic and refuses to believe.
The Shadow evades Batman once again and it isn't until Batman begins to consider that his suspect might be telling the truth that Batman/The Shadow's narrative poetry begins to reveal itself. When Batman, the Shadow and the Stag come face to face, Bruce is forced to grapple with his inability to accept the magic that the other two beings supposedly represent. The Stag is able to escape the encounter, but Batman manages to imprison the Shadow and lock him in the Batcave under Alfred's watch while he plans his next move.
While Batman might not willingly consider the Shadow's backstory, Alfred approaches the man with a much more open mind and is the first to learn the truth about him that's meant to fundamentally change Bruce's future. Henri Ducard, the Shadow explains, was but one of the guises under which he trained Batman, in the same way that he trained countless others who had the potential to become the next Shadow.
The misdirection, lies and secrecy were all part of the Shadow's longest game: Ensuring that Batman would one day succeed him and take on far larger responsibilities than he ever could as Batman. Introducing a Chosen One™ plot line that would potentially give Batman supernatural powers might sound like a middling idea at first, but it begins to feel destined when you look at it as the ultimate tribute to The Shadow's legacy.
As Glen Weldon wrote in The Caped Crusade: Batman and the Rise of Nerd Culture, Bob Kane and Bill Finger ripped off The Shadow to create Batman. This is a thing that people know and a fact that DC's in no real position to deny at this point. What Batman/The Shadow is trying to do, though, is position the Shadow as the thematic ancestor of all these characters, and heal whatever scar tissue might still exist in hardcore Shadow fans' minds by further intertwining the two heroes to one another.