THE day after Thanksgiving in 1985, a priceless work of art disappeared from a gallery in the United States.

The painting, Woman-Ochre by Willem de Kooning, was on display at the University of Arizona Museum of Art in Tucson that day when a middle-aged couple arrived.

The woman quickly struck up a conversation with the guard on duty, while her male companion headed up to the second floor.

Soon after, the man returned again, and the couple left hurriedly.

Suspicious, the guard retraced the man’s steps, only to find no sign of the painting, believed to be worth around $135 million.

The heist occurred in a time before surveillance cameras were the norm, and cops couldn’t find any fingerprints at the crime scene.

So for the next 31 years, Woman-Ochre’s fate remained a mystery.

But last year, a woman named Rita Alter died in a small New Mexico town at the age of 81.

Her husband Jerry Alter had died five years earlier, and it fell to their nephew, Ron Roseman, to clean up their belongings.

Mr Roseman put the house up for sale and antique dealers from Manzanita Ridge Furniture and Antiques arrived from a nearby town to see if any of the Alters’ belongings were worth buying.

David Van Auker later told a news conference he saw “a great, cool mid-century painting” in the home, and the team bought it and the rest of the items in the home for the grand sum of $2715.

Within an hour of staff displaying the painting in the store, a customer claimed it was a genuine de Kooning.

The customer was right — it was a perfect match, and the artwork has since been reunited with its original owners.

But while the Alters’ relatives insist the “quiet” and “pleasant” couple couldn’t have been the real masterminds behind the theft, a mountain of evidence connects them to the crime.

And it seems they may have been dropping clues along the way.

Just a year before he died at 81 in 2012, Mr Alter published a book of short stories titled The Cup and the Lip: Exotic Tales, the Washington Post reported.

One of those stories, The Eye of the Jaguar, features a security guard named Lou, who works at an art museum.

In the tale, Lou is on duty one day when a woman and her teenage granddaughter arrive, and the older woman asks him about a valuable emerald on display.

Half a year later, the pair return to the museum and then abruptly leave, causing Lou to wonder: “Wow, those two seem to be in a hurry, most unusual for visitors to a place such a this”.

After realising the jewel is gone, Lou runs to the street and is struck and killed by the duo’s speeding getaway car, leaving “absolutely no clues which police could use to even begin a search for them”.

The story ends with the emerald left in an empty room: “And two pairs of eyes, exclusively, are there to see” — words which could easily describe the valuable masterpiece that had hung in the Alters’ rural bedroom for more than three decades.

But that’s not the only clue connecting the couple to the theft.

Acquaintances told reporters the Alters owned a sports car similar to one seen leaving the scene of the crime — a car which is also seen in some of the Alters’ home movies, which have been obtained by television station WFAA.

Mrs Alter was also found to have owned clothes which matched the description of the woman at the museum in 1985.

And the normally meticulous couple had left their day planner oddly blank during Thanksgiving in 1985 — a glaring anomaly compared with the rest of their packed diary.

But now, most damming of all, is the discovery of a photo which placed the couple in Tucson at the time of the heist.

Mr Roseman recently found the picture of the couple enjoying a Thanksgiving meal at a family member’s home in Tucson on Thanksgiving day in 1985 — further proof the couple were in the same area at the same time the robbery occurred.

But even in the face of overwhelming evidence, Mr Roseman still can’t quite believe his aunt and uncle stole the painting themselves, instead claiming they had somehow purchased it without realising it’s story.

“They were just nice people,” he told ABC13.

The FBI is investigating the decades-long mystery that has still not been officially solved.