THE MONTH had been disgusting, marked by a foul blanket of air that kept eyes bloodshot, throats tight and comic-book dealer Steve Geppi wondering if, perhaps, The Joker had somehow invaded Baltimore to spread madness and chaos with his deadly laughing gas. Where was Batman when he was needed? It was time, Geppi figured, to flee to the beach.

In the five years since he'd hung up his mailbag and entered the private sector, Geppi, 31, had managed to parlay a few stacks of old comic books into a thriving business trading on the childhood fantasies of grown-ups. Geppi's Comic World was ringing up $150,000 in annual sales buying and selling the adventures of Superman, Batman, Howard the Duck, Archie, Conan and other heroes and villains, new and old, to kids and collectors alike.

He was about to open a Silver Spring store that would give him the luxury of adding heavily to his priceless Golden Age collection. Indeed, the lost innocence of others had been good to Geppi, whose success in nostalgia had recently permitted the move to a new brick three-bedroom house. He felt as if he could leap over it in a single bound.

Geppi figured he had earned a vacation, and asked his store manager to take over. Stop hammering, he told a carpenter who was patching up the house. And he packed off to Ocean City.

Three days later he returned with a tan. But as he walked into the living room, the face turned white. His priceless collection was gone -- Donald Duck, Captain America, The Human Torch -- ripped off, ten boxes worth $40,000.Nothing was insured.

Geppi called the police, warned local dealers to watch out for the hot books and settled in for a long, nervous wait.

The Great Comic-Book Caper was unfolding. It was September 16, 1977.

Why would anyone want to steal comic books?

For one thing, rare old books are worth a fortune, chief among them being the June 1938 Action Comics No. 1, wherein Superman flies for the first time. It lists for $7,500. For another, the heroes and villains evoke childhood dreams the same way songs like "Teen Angel" conjure up memories of crushed velvet, a first kiss, the high-school prom. Comic books reek of the good old days.

Collectors have wars and mothers to thank. The hungry paper drives of World War II gobbled up comics at an astonishing rate. As for mothers, they regarded the likes of Superman as a Mental Menace, and retired such heroes to the dump.

Classic laws of supply and demand began to take hold, and big-time dealers like Geppi started quacking, with Donald, all the way to the bank.

In the last few years, collecting comics has come out of the attic. No longer is it a hobby reserved exclusively for furtive little men in raincoats who slink out of 7-Elevens with Little Lulu in a paper sack. Lawyers, doctors, teachers -- even White House advisers -- are said to slobber over racks of Warlord.

"Comics are the last vestige of American culture the Arabs haven't bought up," says one dealer.

Of course, it makes sense that MeGeneration children would fasten onto vulnerable superheroes like Spiderman, a sensitive super-neurotic, where their parents clung to Superman, a super-stoic. After all, Superman never took responsibility for his tragic flaw -- he blamed every demise on Kryptonite. What he needed was est.

Inevitably, Superman would spawn the selfish era of Megocentrics.

Not that there's anything unhealthy about believing one can fly, tying towels about the neck and jumping off chairs in emulation of the Big S, say psychiatrists. Kids can profit by using just such hero fantasies to foster assertiveness and strength, and make up for a sense of power-lessness.

"There's nothing wrong in identifying with these superheroes," says child psychiatrist Michael Brody. "It's no different than idolizing sports figures like Roger Staubach or Joe Theismann."

But sometimes the fantasy can overstep the most elastic bounds, as it did the other day when Brody had to hospitalize a burly teenager. The boy imagined he was The Incredible Hulk and set to beating on schoolmates and his parents.

Brody anticipates a Superman epidemic this month, when the new movie is scheduled to hit the screen.

And Batman only knows how many fledgling criminals will ride the new comic-book craze, come to take their cues from The Joker... and prey upon hard-working businessmen like Steve Geppi.

AT A SEEDY Wheaton shopping center, Carl Bridgers, 42, was unclogging a human traffic jam about the stacks of 200,000 comics that crowds the aisles of Barbarian Books. Two men approached the counter and plopped down the premiere issue of The Human Torch.

"Wanna buy it?" asked one.

Bridgers, a tall, studious man whose blackrimmed glasses complement a quiet manner, fondled the book and found it to his liking. It was in near-mint condition, and according to the comic-book price guide, the quasiofficial pink sheet for comics, worth $525.

It was a Saturday, t-h-e day for comicbook dealers; the store was packed. Between customers, they haggled. Any other day, the men would have been in and out, and Bridgers would have likely forgotten what they looked like. It took two hours to close the deal.

GEPPI FRETTED, he moaned: no suspects, no leads.

There was only one hope -- The Green Hornet. Geppi phoned Dave Weimer, 36, client, friend and fellow comic-book dealer whose passion for the crime-busting exploits of a 1940s comic-book detective -- The Green Hornet -- have earned him the hero's nickname.

"I got pretty excited when Steve called," said Weimer. "That's a big robbery!"

The Hornet buzzed right over. He narrowed the list of suspects to five -- anyone who might have known Geppi's vacation plans and the address of his new house.

"What about the carpenter?" asked The Hornet.

"Not a chance," said Geppi: "I'd trust the guy with my life."

The Hornet began tailing the suspects in his dark blue Toyota, a car he could easily tuck into the shadows.

"I followed them for two weeks," he said. "I was waiting for someone to move a hot comic. Nothing materialized. It was frustrating."

Making the rounds, though, the Green Hornet wandered into Bridger's Barbarian Books and spied The Human Torch -- Geppi's Human Torch -- imprisoned inside a glass display case.

Bridgers recalled the man who sold him the book as a lanky six-footer with brown hair.

BEHIND THE green mask he sometimes wears, The Green Hornet has a receding hairline. He's a chunky six-footer, his thinning, dark-brown hair laced with gray.He has served in the Army, been married three times, managed a department store. Nowadays he deals in comics, but he still dreams of becoming a cop, his desire fueled by lawmen he has come to idolize -- in comic books.

"In comics," he says, "life is cut-and-dried, crimes are solved. You get answers to all your questions. The good guy may have a tough time, but he always wins."

The only son of a college religion professor who served in Germany with Patton, The Hornet didn't see his father until he was seven years old. "It had a devastating effect on me," he says. "I used comics as an escape from reality, to find people I could relate to."

The Green Hornet reads Matt Helm, Ian Fleming and Harold Robbins, smokes a pipe and favors a blue bathrobe when he stays up late to watch Carson and Snyder. "I just think better at night," he says.

And he was thinking hard when he got the call. It was 10 p.m.

"Would you like to buy some comics?" asked the voice.

Out of the blue, the voice said that a stranger he'd met at a wedding heard him talking about his hobby, comics, and handed him Weimer's business card. The card indicated Weimer bought comics. The voice had a few to sell. He said his name was Walter Willis, 31; his trade, carpentry. They agreed to meet.

THE CARPENTER laid a handful of rare books on the table. He'd gotten the books from a friend, he said, cheap. The Green Hornet took cruel delight in turning the conversation to Geppi's yetunsolved comic-book ripoff -- much talked-about in comic-book circles.The carpenter. gave a nervous laugh and agreed it was too bad.

From a hidden perch on the staircase, Baltimore County Detective Bruce Magladry heard it all.

The Green Hornet liked what he saw, picked out two Captain Americas, one Donald Duck and counted out $200 in marked bills. The two comic-book connoisseurs shook hands.

As the carpenter's cream-colored van pulled out of the driveway, Magladry's partner, Detective Jim Tinscher, hit his red light. A mere 30 comics were found in the back -- among them three belonging to Geppi, who later proved ownership by producing ads that noted such defects as a slight tear, bottom corner, page 32.

To the collector, every book has its fingerprint.

Willis denied stealing the comics. He told police he'd gotten them from "an old man he'd worked with on a house." He refused to name names; he didn't want to get anyone in trouble.

Another dead end. Geppi was still out $39,800 worth of comics.He offered a $1,000 reward. The story of the caper hit local papers. A woman phoned the police. She had some information.

THE DETECTIVES obtained a search warrant and paid the Willis home a visit. They scoured the house: nothing. They searched the attic: nothing. On the way out, Tinscher nearly tripped over an ill-fitting floorboard.

"Mr. Willis, would you please pull that up?" he asked.

The carpenter pried up the board. Underneath were comics -- thousands of comics between the joists, stacks of comics laid neatly atop the insulation.

"Well," shrugged Willis. "You got me."

EPILOGUE

The carpenter who coveted his neighbor's comics pleaded guilty. He was sentenced to 18 months' probation.

The Green Hornet split the $1,000 reward with the tipster, and wore his Green Hornet mask and T-shirt to the station to help Geppi load up his comics.

The carpenter was also ordered to reimburse Geppi for the unrecovered comics and the reward -- in effect, to pay for his own capture.

The two detectives have yet to shake the nicknames Batman and Robin.

A footnote: Just the other day, crooks hit The Green Hornet's store in Belair for $5,000 worth of comics. He is distraught. After all, what's a famous crime-buster to do when he needs help?

"It looks like another case for The Green Hornet," says Weimer. "I need him more than ever."