Missing mum Nicola Bulley vanished on a dog walk along a remote riverbank 13 days ago.
Despite a major search effort, police admitted yesterday no significant evidence has been found to prove what actually happened.
The 45-year-old had dropped her two children off at school in St Michaels on Wyre on January 27 before taking springer spaniel Willow along a river towpath.
However, her phone was later found on a bench overlooking the water, with the dog wandering alone nearby.
A major police operation has been launched, with an independent under forensics team also drafted in this week.
Police have ruled out third party involvement and yesterday extended the search to the sea - but there are still no concrete clues about what happened to her.
Below is a rundown of the facts and the key questions that still need answering...
Nicola's last known movements
As part of the public appeal, police released a timeline of Nicola's movements during her walk.
At 8.26am on Friday, January 27, Nicola left her home in Inskip with her two daughters, aged six and nine, dropping them off at school and engaging in a brief conversation with another parent around 15 minutes later.
Doorbell camera footage was released showing her outside the family home loading the dog into the boot.
Leaving her car park at the school, she took Willow for a walk at 8.43am along the river path.
She was seen by a dog walker who knew her at around 8.50am and at 8.53am sent an email to her boss.
It's understood she then texted her friend about meeting up later in the week at 8.57am and then logged into a work conference call at 9.01am.
She was seen by a second witness at 9.10am, the last known sighting.
Phone and dog found - but no sign of Nicola
Despite her last known sighting being in a field, Nicola's phone was found back down the route on a bench at 9.33am.
Another dog walker came through a gate and found Willow wandering alone without her harness on, which was on the floor - then spotted the phone.
Willow is described as being agitated, but friends said it was common for Nicola to remove her harness to let her roam around while she waited nearby.
It is understood the unnamed dog walker was able to get a message to Nicola's partner Paul and he headed to the scene before reporting her missing to the police.
This was done around 10.50am.
Underwater forensics specialist Peter Faulding - who is involved in the scouring the river - has suggested the phone may have been placed on the bench as a decoy.
Search launched
A major search effort was launched that morning, with Bowland Pennine Mountain Rescue drafted in around midday.
Led by Kev Camplin, a team of 25 trained search volunteers, joined police specialists until it got dark.
Their efforts included searching the grounds of a large country home, which they initially presumed was empty.
However, someone identifying themselves as the property owner agreed to search inside but didn't find Nicola.
The following day, police drones, helicopters and dogs, as well as fire and rescue services and an underwater search team were at the scene.
And on the Sunday (January 29), residents met at the village hall around 10.30am before organising two separate searches in the morning and afternoon.
Police warned volunteers to be cautious, describing the river and its banks as "extremely dangerous" and saying that activity in these areas pose "a genuine risk to the public".
Police speak to witnesses
In the first press conference on Monday, January 30, Superintendent Sally Riley said her colleagues were "keeping a really open mind about what could have happened", and that they're not treating Nicola's disappearance as suspicious.
Investigators released the CCTV image of a potential witness - a man in his 70s - the following day and he was spoken to.
Days later a second witness was sought - 68-year-old Christine Bowman - who was then tracked down but said she was baffled as she'd already given officers a statement.
A third witness, a woman pushing a baby in a pram, was also sought.
Family speaks out
Nicola's parents, Ernest and Dot Bulley, spoke to The Mirror on February 1 about the "horror" they faced over the possibility of never seeing her again.
Her father said: "We just dread to think we will never see her again, if the worst came to the worst and she was never found, how will we deal with that for the rest of our lives."
They were then joined the following day on TV by daughter Louise Cunningham.
Two days later Nicola's partner Paul spoke in a separate televised interview.
Police hypothesis
On Friday, Superintendent Riley said the main hypothesis was that Nicola had fallen into the river.
She warned the public against speculation, saying it's "possible" that an "issue" with Nicola's dog may have led her to the water's edge, such as dropping a ball in the water.
Nicola's friends rubbished this claim, saying they rarely took the ball on walks and she wouldn't have tried to fish it out, putting herself at risk.
Police have also made clear there is no evidence supporting their main theory, including any slip marks at the scene.
Nicola is also described as a strong swimmer and despite a pool in the middle of the section of river going down 18ft, there was not thought to have been a strong current at the time.
Supt Riley reiterated this line of thinking yesterday and ruled out foul play.
She added that the search has been extended to the estuary and sea at Morecambe.
Dive expert's theory
Specialist Group International (SGI) were drafted in on Monday and have spent two days searching the river using special sonar equipment.
Dive chief Peter Faulding initially said his team would find Nicola in under an hour if she had fallen into the river at the bench.
He speculated if she had drowned her body would have become snagged and would have got stuck within 500 metres.
Mr Faulding was adamant she wouldn't have drifted out to sea.
But after failing to find her, he began to speculate that she may have been abducted.
