The Gioconda Caper by Bob Shaw

The Gioconda Caper by Bob Shaw (Cosmic Kaleidoscope, 1976) opens like a hardboiled detective story, but quickly becomes something else:

It was a Thursday morning in January—stale and dank as last night’s cigar butts—and my office phone hadn’t rung all week. I was slumped at the desk, waiting out a tequila hangover, when this tall, creamy blonde walked in. The way she was dressed whispered of money, and what was inside the dress hinted at my other hobby—but I was feeling too lousy to take much notice.
She set a flat parcel on my desk and said, “Are you Phil Dexter, the private psi?”
I tipped back my hat and gave her a bleak smile. “What does it say on my office door, baby?”
Her smile was equally cool. “It says Glossop’s Surgical Corset Company.”
“I’ll kill that signwriter,” I gritted. “He promised to be here this week for sure. Two months I’ve been in this office, and. . .”
“Mr. Dexter, do you mind if we set your problems on one side and discuss mine?” She began untying the string on the parcel.

The woman, Caroline Colvin, then unwarps the parcel and shows him a very good copy of the Mona Lisa—but the hands seem in a slightly different position and, when Dexter touches it, he gets an impression of great age, hilly landscapes, and a bearded man standing in front of a carousel-like contraption. Dexter rapidly comes to the conclusion that the painting is by Da Vinci himself.
Dexter then learns that Colvin inherited the painting from her father, who had visited Italy the previous spring. When he touches the painting again, he senses that her father recently travelled to Milan—the pair are soon catching the noon sub-orbital to the city.
Once they arrive in the city, it isn’t long before Dexter’s psi abilities enable him to track down a man called Crazy Julio, something Dexter manages with the help of a highly dodgy waiter called Mario (who, when he isn’t trying to buy Colvin from Dexter for the white slave trade, is gouging Dexter for money and rewinding the speedometer on the car he has borrowed from his mother).
The last part of the story sees Dexter and Colvin drive the last two miles to Crazy Julio’s without Mario as Dexter doesn’t want the waiter to get wind of the Mona Lisa, or the potential money involved (Dexter comments to Colvin, “If that poor boy isn’t in the Mafia, it’s because they gave him a dishonorable discharge.”).
When the two of them finally arrive at Julio’s farmhouse he greets them with a shotgun, but Dexter soon overcomes his resistance:

“Come on, Julio.” I got out of the car and loomed over him. “Where is the cave?”
Julio’s jaw sagged. “How you know about the cave?”
“I have ways of knowing things.” I used quite a lot of echo chamber in the voice, aware that peasants tend to be afraid of espers.
Julio looked up at me with worried eyes. “I get it,” he said in a low voice. “You are pissy.”
“P-S-I is pronounced like ‘sigh,’ ” I gritted. “Try to remember that, will you? Now, where’s that cave?”

In the cave (spoiler) Dexter and Colvin discover that they are another fifty or sixty Mona Lisa paintings loaded on a merry-go-round-like device with a viewing lens attached. Dexter realises that it must be some sort of animation device, and gets Julio to turn the crankshaft while he watches:

On top of everything else that had transpired, I was about to have the privilege of actually viewing Leonardo’s supreme masterpiece brought to magical life, to commune with his mind in a manner that nobody would have thought possible, to see his sublime artistry translated into movement. Perhaps I was even to learn the secret of the Gioconda smile.
Filled with reverence, I put my eyes to the viewing holes and saw the Mona Lisa miraculously moving, miraculously alive. She raised her hands to the neckline of her dress and pulled it down to expose her ample left breast. She gave her shoulder a twitch, and the breast performed the classiest circular swing I had seen since the last night I witnessed Fabulous Fifi Lafleur windmilling her tassels in Schwartz’s burlesque hall. She then drew her dress back up to its former position of modesty and demurely crossed one hand over the other, smiling a little.
“Oh, God,” I whispered. “Oh, God, God, God, God!

The last scene has the complication of Mario turning up at the cave and getting the drop on them. Initially he is only interested in the immense wealth that will be his but, after viewing the animation, burns the paintings and mechanism out of an upwelling of national pride.
An amusing story with a clever (and certainly different!) central gimmick.
***+ (Good to Very Good). 7,650 words. Story link.