It is no bigger than a sliver of shadow.
But that faint bulge - a subtle band pressing against a gloved pinky finger - is fast becoming one of the most talked-about clues in the chilling disappearance of Nancy Guthrie.
Three weeks into an increasingly frantic search for the 84-year-old mother of NBC Today co-anchor Savannah Guthrie, investigators are zeroing in on a detail that could provide a much needed break in the case: a pinky ring apparently worn by the masked man caught on doorbell camera footage the night she vanished.
The grainy video, recorded on the porch of Guthrie's $1million ranch-style home just north of Tucson, Arizona, shows a man in a ski mask, backpack, jacket and gloves.
He approached the front door and reached toward the camera with his right hand. In that split second, a band-shaped imprint appeared beneath the glove on his little finger.
The Daily Mail spoke with three former law enforcement officials who agreed that even such a small detail could help narrow the hunt for the suspect in what authorities are investigating as an alleged kidnapping.
At the very least, they said, the presence of a ring on the pinky could help detectives prioritize leads.
In a case flooded with tips - more than 28,000 phone calls between February 1 and 16, a 54 percent spike over the same period last year - triage is critical, said Lance Leising, a former FBI supervisory special agent based in Arizona.
Police are now looking at a suspected pinky ring that they believe Nancy Guthrie's alleged kidnapper was wearing in the doorbell footage
Nancy Guthrie was reported missing on February 1 from her home in Tucson, Arizona
'If a tip identifies someone who matches the description and investigators see a pinky ring in social media posts, that would make that tip a higher priority and more resources would be applied,' he said.
Leising cautioned that he was not certain the video is definitive. The footage is grainy, the lighting is poor, and what appears to be a jewelry band could be a fold in the glove.
But in a case like this, he added, every detail is 'useful.'
Pinky rings are not common - and that makes them distinctive.
Gregg Etter, a criminology professor at the University of Central Missouri and a 29-year law enforcement veteran, called the ring a potential 'trait' that could move a suspect to the top of the list.
When detectives are chasing down leads and perhaps a dozen individuals merit closer scrutiny, he said, the man known to wear a ring on his right pinky suddenly becomes more interesting.
It is not proof, it is not probable cause, but it is a filter.
'Anything can be useful as a clue,' said Daniel Brunner, a 29-year veteran FBI special agent. 'Nothing can be not considered.'
The focus on that tiny band of shadow comes as the search for Guthrie stretches into its 18th day with no arrests.
Guthrie was reported missing on February 1 after spending the previous night with family.
Blood was later detected on the porch of her secluded home in the upscale Catalina Foothills community.
New York mob boss John Gotti is among the gangsters who wore a ring on their pinky
The FBI has said the suspect appears to be about 5ft, 9in tall with a medium build.
Every frame of the porch video has now been pored over by investigators - and by legions of online sleuths - and the moment the masked man reached up to tamper with the camera has become a tipping point in the case.
Reddit threads and Facebook groups have exploded with theories. Some users claim the bulge resembles a simple wedding band, while others argue it looks thicker - perhaps a signet ring.
Some have attempted to estimate the height of the ring's setting from the distortion of the glove fabric.
Pima County Sheriff Chris Nanos has acknowledged the speculation.
'I look at the same photo you look at and I get. I see it. I see,' Nanos told NBC News this week.
He said investigators would 'analyze' the clue while noting that it remains an area of 'speculation.'
Still, speculation can guide inquiry. Leising suggested that the ring could even point investigators toward specific organized groups known to wear pinky rings.
'If you identify organized groups that wear a ring on the right pinky, that would be a good group to investigate and identify members,' he said.
Historically, pinky rings have been associated with organized crime figures - famously worn by mob boss John Gotti, as well as fictional gangsters like Tony Soprano and Michael Corleone.
Modern criminal organizations, including some Central American drug cartels, are known for conspicuous jewelry and displays of wealth.
Etter said he was unaware of any strong current preference for pinky rings among major gangs, but acknowledged that jewelry can serve as a symbol of affiliation or status.
Pinky rings are also a hallmark of Freemasons and other fraternal organizations
But it is not just applicable to gangsters. Members of fraternal organizations such as the Freemasons have long worn pinky rings, and aristocratic families have passed down signet rings bearing crests for generations.
Engineers in North America sometimes wear simple iron or steel bands. Some geologists sport silver rings. Graduates of the Canadian Institute of Forestry are known to wear distinctive bands, too.
It is a wide net - perhaps too wide. But in a case where false dawns have already come and gone, investigators appear willing to chase even remote possibilities.
On Saturday, hope briefly flared when a Special Weapons and Tactics team raided a home near Nancy Guthrie's residence.
Authorities searched a gray Range Rover and detained the driver. Multiple individuals were questioned. No arrests were made.
Another potential breakthrough emerged when law enforcement recovered a glove near Guthrie's property that appeared similar to the one worn by the masked man in the video.
But Nanos later said the glove yielded no new leads. It failed to match the Combined DNA Index System, the national database of DNA profiles.
The investigation is being led by the Pima County Sheriff's Office alongside the FBI.
Sources have told TMZ that authorities are considering the possibility that Nancy Guthrie was taken across the border into Mexico.
The sheriff's office has acknowledged reports of coordination with Mexican authorities but declined to confirm specifics.
Nancy Guthrie was last seen on the night of January 31 after going to her eldest daughter's house for dinner and a game night
Savannah Guthrie shared a somber video online, begging her mother's captors to 'do the right thing'
Through it all, one question looms: Is Nancy Guthrie still alive?
'They ask me, do I have proof of life? I ask them, is there proof of death?' Nanos said earlier this week.
For Savannah, the agony is public and relentless. In an Instagram video posted Sunday, she appealed directly to anyone with information.
'It is never too late to do the right thing,' she said. 'And we are here. And we believe in the essential goodness of every human being, that it's never too late.'
Back on the porch of that Catalina Foothills home, investigators are still studying the footage: a masked man, a gloved hand, a shadow on a pinky finger.
In a case defined by absence - no body, no arrest, no clear suspect - that small, stubborn detail may yet prove decisive.
