The video was taken by a disabled doorbell camera. They show a person wearing a ski mask, gloves and a backpack early on the morning of Feb. 1.
Here is a timeline of the major developments in the case.
9:48 p.m., Jan 31.
Just after 5:30 p.m., Ms. Guthrie took an Uber to the nearby home of her older daughter, Annie, and her son-in-law, Tommaso Cioni. The three spent about four hours together, eating dinner and playing games, before Mr. Cioni drove her home.
Ms. Guthrie's garage door opened at 9:48 p.m. and closed two minutes later, according to the authorities. Mr. Cioni watched to make sure Ms. Guthrie made it safely inside. That was the last time anyone in her family saw or heard from her.
1:47-2:28 a.m., Feb. 1
Ms. Guthrie's front door camera was disconnected at 1:47 a.m. About 25 minutes later, a camera somewhere on her property detected motion, but recorded no video, because she did not have a subscription to the device's service provider.
At 2:28 a.m., about 15 minutes after the camera was set off, Ms. Guthrie's pacemaker lost contact with her cellphone, which investigators would later find inside the house, suggesting this may have been about the time she was taken.
Feb. 1, morning
When Ms. Guthrie did not arrive at a friend's house to watch a live-streamed church service on Sunday, the friend notified Ms Guthrie's family. Family members went to her house just before noon to check on her, discovered she was missing and called 911.
The authorities found her phone, wallet, hearing aid, daily medication and car. At her front stoop, they found an empty mount where a doorbell camera had once hung, and on the tile below they saw spatters of blood, which DNA analysis later confirmed to be Ms. Guthrie's.
Sheriff Chris Nanos of Pima County, Ariz., told The New York Times that investigators found even more worrying signs of violence at Ms. Guthrie's home. "There were things at that home that were of concern," he said. "That scene, there were things that, I thought, this doesn't sit well."
He declined to elaborate, but investigators spent the week combing through the home, its garage and the surrounding scrubland.
Feb. 2
Roughly 24 hours after the sheriff's department first posted a missing-person bulletin for Ms. Guthrie, a Tucson television station, KOLD, received a note claiming to be from her kidnapper. The station forwarded it to the authorities.
The celebrity gossip site TMZ, which received a copy the next morning, reported that the letter demanded millions of dollars in Bitcoin for the release of Ms. Guthrie. Harvey Levin, the outlet's founder, described the letter on a broadcast as "very well constructed."
Feb. 3
As investigators acknowledged that they had few answers about who may have kidnapped Nancy Guthrie, NBC Sports said Savannah Guthrie would not be part of the network's coverage of the Winter Olympics in Italy. Mary Carillo took her place alongside Terry Gannon as a host of the network's coverage of the opening ceremony on Friday.
Savannah Guthrie also has been absent from the "Today" set to be in Tucson with her family. Hoda Kotb, her co-anchor on "Today" from 2018 until 2025, returned to the show to fill in for her former colleague.
Feb. 4
Ms. Guthrie's children recorded their first emotional address to their mother's kidnapper and posted it to Savannah Guthrie's Instagram account. Savannah Guthrie, trying to hold back tears as she read from a paper, said her family had heard about purported ransom letters that had been sent to news organizations.
She said that they wanted to hear directly from anyone who may have taken their mother, but that they first needed proof she was alive.
"We are ready to talk," she said, flanked by her older siblings, Annie and Camron Guthrie. "However, we live in a world where voices and images are easily manipulated. We need to know, without a doubt, that she is alive, and that you have her."
Feb. 6
KOLD received another message from the supposed kidnappers. The message, which the station forwarded to the police and did not describe publicly, came from a different IP address than the ransom note, but the senders appeared to have used the same methods to mask their location and identity, the station said.
Harvey Levin, the founder of the celebrity gossip site TMZ, which received a copy of the note the next morning, said it did not come with proof that Ms. Guthrie was alive, but it did begin by saying she was "safe but scared."
The next day, the Guthrie siblings released another video. It was 20 seconds long and cryptic. Savannah Guthrie, speaking without a visible script, said into the camera: "We received your message, and we understand. We beg you now to return our mother to us so that we can celebrate with her. This is the only way we will have peace."
Feb. 9
As the search entered its second week, Savannah Guthrie implored the public for help in finding her mother, saying in an Instagram video that she and her siblings believed that she was "still out there."
New images and videos released on Tuesday showed a masked, armed person at Nancy Guthrie's doorstep on the night she was abducted, the first significant break in the investigation.
The black-and-white footage, released by the F.B.I. and the Pima County Sheriff's Department, depicts a person wearing a ski mask, gloves, a backpack and what appears to be a holstered handgun outside Ms. Guthrie’s home, just north of Tucson. Investigators said the person was armed.
Late in the day, the authorities detained a main for questioning in the case but released him early on Feb. 11. In an interview, the man said he had not heard about Ms. Guthrie’s disappearance but hoped that she would be found safe. “I hope they get the suspect,” he said, “because I’m not it.”