The light is dim. The air is cold. The long cement hallways stretch on and on, 85 feet underground. Every footstep echoes.

It's the perfect place for a mystery — or for an archive devoted to solving them.

Tim Johnson leads the way. He is the curator of the University of Minnesota's Sherlock Holmes Collections, the largest archive of its kind in the world.

The massive collection, which contains more than 60,000 items related to the fictional detective, is housed in the underground caverns of the University's Elmer L. Andersen library.

The caverns were carved right into the limestone bluffs along the Mississippi River in Minneapolis. They're kept at a chilly 62 degrees to preserve the rare materials they hold. The complete absence of natural light makes it easy to lose track of time.

"I've brought mystery writers on this tour," Johnson says. "They tell me it would be a great place to find a body."

The only bodies this time are on the pages of Sir Arthur Conan Doyle's stories. In a room off one of the long passages sits the largest trove of Sherlock materials ever compiled — first editions, manuscripts, correspondence. But it isn't just an archive of Conan Doyle's original work, it's a record of Sherlock's status as a pop culture icon. That means there are board games and giant stuffed rats and crocheted odes to the detective.

"Yes, crochet," Johnson says, reading off the labeled boxes. "Sherlock ceramics, teapots, crochet. Handguns. We actually have two handguns. Towels."

The eclectic collection has everything from an original page of "The Hound of the Baskervilles" to a porcine version of the detective: Sherlock Hams.

Tim Johnson, the E. W. McDiarmid Curator of the Sherlock Holmes Collections, showed off Sherlock Hams. Tracy Mumford | MPR News

But how did the world's largest Sherlock Holmes collection end up 4,000 miles away from 221B Baker Street, buried underneath the University of Minnesota?

Elementary, my dear Watson: Devoted Minnesota fans hatched a plan in the 1970s to make the state a Sherlock nexus.

(And, for the record, you won't find the phrase "elementary, my dear Watson" in any original Sherlock book. It comes from later stage and film adaptations.)

The start of the case

When Conan Doyle's first Sherlock Holmes story went to print in 1887, the eccentric detective was an instant sensation. Bands of loyal readers sprung up around the globe, forming their own societies devoted to all things Sherlock.

In 1934, The Baker Street Irregulars formed in New York City, and by 1947 the fervor had reached Minnesota. Five University of Minnesota professors formed their own offshoot of the Irregulars, calling themselves the Norwegian Explorers. They dedicated themselves to "keeping green the memory of the master, Sherlock Holmes, and honoring his creator, Sir Arthur Conan Doyle." (The group is still active today.)

These five founding Sherlock fans — which included two deans, two chemistry professors and the University's head librarian — set the plan for the archive in motion.

Among the five, E.W. McDiarmid was the true culprit behind the collection — the one to point the finger at, the mastermind at work. It was he who hinted to the University's longtime curator, Austin McLean, that it would be nice for the University to have on its shelves a first-edition set of the Sherlock stories.

They finally bought a set at auction in 1974. It was known as the Iraldi Collection. It contained 160 volumes in all, and it opened the floodgates for Minnesota.

The Hench Collection poured in next, in 1978. It had been compiled by Dr. Philip Hench, a Mayo Clinic rheumatologist and a 1950 Nobel laureate. Together with his wife, Mary Kahler Hench, he had amassed an extensive collection of "Sherlockiana": manuscripts, artwork and more.

"All of a sudden," said Johnson. "The Sherlockian world sat up and took notice about what's going on in Minneapolis."

Dorothy Rowe Shaw's miniature replica of Sherlock's sitting room sits in the library offices, complete with a tiny pipe and a bearskin rug. It took six years to assemble. Tracy Mumford | MPR News

A league of allies

With these two large acquisitions, the University became a draw for ardent fans. They visited for conferences, such as 1974's lecture, "The Cult of Sherlock Holmes."

One of the visiting speakers was John Bennett Shaw, who was rumored to have the largest private Sherlock collection in the world.

"I have a room that was built just to house my collection," he told the audience. "And I must report that it's almost full and I don't know what I'm going to do."

Shaw was a very different collector than the Henches. While the Henches collected the high points, Johnson said, Shaw had "the collecting mentality of a vacuum cleaner: Anything and everything to do with Holmes, he collected it."

Won over by what he saw developing in Minnesota, Shaw decided that, upon his death, his collection would join the growing trove at the University. It included 9,000 books alone, not to mention the magazines, photographs, films, recordings, crafts and costume pieces. He went on to persuade others to donate their collections, as well.

Shaw won over Edith Meiser, a writer and actress with an occasional role on "I Love Lucy." Meiser wrote and recorded Sherlock radio plays in the 1930s and '40s, and her collection included original scripts and recordings on 16-inch transcription discs.

With Shaw's and Meiser's collections secure, the size of the archive more than doubled, turning it into a "critical mass with its own gravitational field that pulled in even more," Johnson said.

The chase continues

Now the largest in the world, "the mission of the collection has changed from just trying to acquire the basic materials surrounding the original stories to now trying to document Holmes as popular culture icon." Hence the archive's cartoon Sherlock wallpaper and Bearlock Holmes, the teddy bear detective. Currently, they're hoping to get original scripts from the set of the new BBC adaptation, starring Benedict Cumberbatch, Johnson said.

Johnson himself was first lured to Minnesota not by the promise of Sherlockiana, but by the university's other rare collections. Once he arrived, however, his lifelong love of Holmes made him an obvious choice to steer the detective's collection.

In 2010, he was named the first-ever E. W. McDiarmid Curator of the Sherlock Holmes Collections, an endowed position made possible by the The Friends of the Sherlock Holmes Collection. He now spends half of his time devoted solely to Sherlock. He sorts through the collection, speaks to visiting groups, organizes programming and catalogs the 300 to 500 new Sherlock items that arrive every year.

Johnson's two favorite items in the collection are, at the moment, out of the caverns and off on tour: the original manuscript page from "The Hound of the Baskervilles" and a set of Sherlock books once owned by the Czarina Alexandra of Russia.

"After the Russian royal family was executed, the communists sold off their library," Johnson said. "They have her bookplate. You open them and you know they were owned by the last czarina of Russia."

The archive's next adventure

A close-up of the last czarina of Russia's personalized bookplate, inside her copy of "The Memoirs of Sherlock Holmes." Courtesy of the University of Minnesota

The Sherlock collection is not on display for the public, but the university does host guided tours on occasion. Most of the items never leave the caverns, but many have been digitized and can now be accessed online.

Every three years, the university, in partnership with the Friends group and the Norwegian Explorers, arranges a conference to celebrate the developing scholarship around the detective. The next one is scheduled for July 2016: "The Misadventures of Sherlock Holmes."

And, as Johnson said, there's no telling what might be down in the caverns by then.

Obscure treasures from the Sherlock archive