Nicola Bulley was last seen walking her dog in a field by a river more than three weeks ago.

She had just dropped her two girls off at school in town at St Michael's on Wyre in Lancashire, a county in north-west England. 

Ms Bulley, a 45-year-old mortgage adviser, then took her springer spaniel Willow for a wander along the River Wyre.

She sent a few messages, one of them organising a play date for her children, and logged into a work call on Teams at 9:01am. 

Her microphone was muted and her camera was switched off during the call, something Lancashire Police say was not unusual for the mother of two.

About 20 minutes later, another dog walker found Ms Bulley's phone on a bench next to the river, still logged into her call.

Willow was seen running between the bench and a gate into the field.

But there was no sign of Ms Bulley. 

She was officially reported missing about an hour and a half later, with police immediately grading her as a high-risk missing person based on the vulnerabilities her partner Paul disclosed to officers. 

Cue an extensive search party — and internet sleuthing. 

What happened to Nicola Bulley?

Police say they don't know for sure, but the most likely scenario is she fell in the river. 

Detective Superintendent Rebecca Smith is leading the investigation into Ms Bulley's disappearance.

At a press conference on Wednesday, 20 days into the investigation, Superintendent Smith said police were working on a number of hypotheses, including:

• Ms Bulley may have gone into the river
• There may have been third-party involvement in Ms Bulley's disappearance
• Ms Bully may have left the area voluntarily 

Superintendent Smith said, based on all the facts, her main working line of enquiry was "that Nicola had gone in the river".

"That does not mean that we aren't continuing to investigate every single line of enquiry because I can assure you, we are," she said. 

"I cannot be one 100 per cent certain of that [hypothesis] at the minute because we are continuing … It's a live investigation and there is always information coming in but we are in the 20th day." 

She said police had always been "open-minded" about what happened to Ms Bulley and those three hypotheses were being "continually reviewed". 

"At the minute, with the information that we have received and reviewed, there is not a single piece of information of evidence to suggest that there is any third-party involvement in this investigation," she said. 

Police say there's been nothing to suggest criminal activity. 

And they say that, based on CCTV and dashcam footage and other evidence, "there is nothing to suggest that Nicola left the field".

But the chatter on social media favours other theories.

'Conspiracy theories' and 'social media sleuths' 

As Ms Bulley's disappearance continued to attract attention in the press, people following the case began to speculate online about what happened. 

A report from BBC disinformation and social media correspondent Marianna Spring said a string of "amateur social media sleuths" descended on the area. 

They flocked to the town to do their own investigating, like something from an episode of Only Murders In The Building — a fictional television series about three true crime podcast fans solving a mystery after mistrusting the police. 

"Tourists travelling to scenes of disappearances are nothing new — nor are true crime sleuths online," Spring wrote. 

"But the frenzy on social media — and TikTok in particular — seems to be sucking in a huge number of people."

A week before Wednesday's press conference, police issued what's called a dispersal order in St Michael's on Wyre. 

Here's the police statement about that: 

"This followed reports of individuals — from outside the area of St Michael's — filming on social media close to properties.

"The order will remain in place for 48 hours and gives officers the power to disperse anyone committing anti-social behaviour.

"Two dispersal notices were issued, and a number of other people were warned about their behaviour.

"We hope that will give people some reassurance that we will not tolerate criminality, including trespass and criminal damage.

"We are also aware of a number of grossly offensive comments being made on social media and elsewhere. We are looking into these and will not hesitate to take action where appropriate."

A few days later, police posted on Twitter, pleading for an end to the online speculation:

"There is also a huge amount of commentary from so-called experts and conspiracy theories which are damaging to the investigation and, worst of all, to Nicola's family.

"It must stop."

Press conference addresses 'TikTok detectives'

Superintendent Smith said "TikTokers have been playing their own private detectives" in this case. 

And she said this had significantly distracted the investigation.

"In 29 years in the police service, I've never seen anything like it," she said. 

"Some of it's been quite shocking and really hurtful to the family. 

"Obviously we can't disregard anything and we've reviewed everything that's come in but, of course, that has distracted us significantly.

"But as long as we are prioritising, which we are doing constantly, on the information that's coming in, that will not distract us from the priority actions that we have been completing."

Superintendent Smith said police had been "inundated with false information, accusations and rumours". 

She was joined by Assistant Chief Constable Peter Lawson, who said "ill-informed speculation and conjecture" had impacted the investigation. 

"We've shared more detail in this conference than would normally be the case," he said.

Myths: the red van, the fishermen and the derelict house

Superintendent Smith made a point of ruling out a series of "persistent myths" about the case. 

Here's a quick rundown of some of those and what Superintendent Smith said about them:

The derelict house:

There were questions about a derelict house which is across the other side of the river.

"That has been searched three times with the permission of the owner and Nicola is not in there."

The red van:

There were reports of a red van in the area at that time.

"The red van … it has been reported that it was in the area on the morning of the 27th, like many other hundreds of cars that morning.

"We're really grateful for the witness who has told us about that and we are continuing to make enquires to try and track down that specific van.

"But from my perspective, being in possession of all the facts and information of this case, I do not believe that to be suspicious.

"But we are continuing to investigate that so that we can identify whoever was in the area that time to make sure they can't give us any further information that will assist the investigation." 

The glove:

A glove was found in the area. 

"That is not believed to be relevant to the investigation. 

"It is not Nicola's but we have got that in our possession."

The fishermen:

Superintendent Smith said there were some fishermen in the area, "who were described as suspicious". 

"I myself don't find it suspicious that fisherman would be in an area of a river that morning or carrying fishing rods. 

"But there was some suggestion that one of these males might have been looking to cover his face.

"We have made numerous appeals for these fishermen to come forward.

"We have made contact with the local angling clubs and we have also ascertained the time of the witness passing down that road and checked the CCTV at The Grapes pub, which covers that end of Garstang Road. 

"And we can't see any of those fishermen at the time on that day.

"But we are continuing to try and trace these people. 

"Again, I would urge that they are not necessarily suspicious to me, but I'm really keen to trace them to make sure that there's no further information that they can give us that will assist."

The Fitbit

Police said Ms Bulley was wearing a pale blue Fitbit — a digital fitness tracker that resembles a wristwatch — when she disappeared. 

But there's been no data received from that because it hadn't been synced "for a number of days". 

Why was Nicola Bulley graded as 'high risk'?

That was the first question the police officers were asked at the press conference. 

"I'm not going to go into the details of those individual vulnerabilities," Superintendent Smith said. 

"I've asked you to respect the family who are going through unimaginable pain and distress at this moment. 

"But those vulnerabilities based our decision-making in terms of grading Nicola as high-risk and have continued to form part of my investigation throughout."

But later that day, the Lancashire Police put out a statement.

Nicola Bulley's 'vulnerabilities' revealed

The police statement summed up the content of the press conference, but revealed details the investigators declined to disclose earlier that day. 

Here's what it said:

"We have described how Nicola had some vulnerabilities at the time she went missing and we just wanted to expand on that a little.

"Sadly, it is clear from speaking to Paul and the family that Nicola had in the past suffered with some significant issues with alcohol which were brought on by her ongoing struggles with the menopause and that these struggles had resurfaced over recent months.

"This caused some real challenges for Paul and the family.

"As a result of those issues, a response car staffed by both police and health professionals attended a report of concern for welfare at Nicola's home address on January 10th.

"No one has been arrested in relation to this incident, but it is being investigated.

"It is an unusual step for us to take to go into this level of detail about someone's private life, but we felt it was important to clarify what we meant when we talked about vulnerabilities to avoid any further speculation or misinterpretation.

"We have explained to Nicola's family why we have released this further information and we would ask that their privacy is respected at this difficult time."

Police under fire

Police were criticised over the decision to reveal Ms Bulley's "vulnerabilities", with many saying the revelation breached her privacy. 

A former victims' commissioner for England and Wales, Vera Baird, told the BBC she didn't think police would share similar comments if Ms Bulley was a man. 

"Would we have had police officers saying … he's been unfortunately tied down with alcohol because he's been suffering from erectile dysfunction for the last few weeks? I think not," she told the broadcaster.

"No, it is a dreadful error to put this in the public domain for absolutely nothing and I'm afraid I think it's as sexist as it comes.

"It's going to undermine trust in the police yet further."

The Lancashire Police reported itself to the Independent Office for Police Conduct (IOPC) over the contact it had with Ms Bulley before she disappeared. 

According to a BBC report, Lancashire Police said this referral was only related to the interaction with the family, not the missing person investigation.

Metropolitan Police Commissioner Mark Rowley told LBC that revealing this level of detail was "rare" for police, but there might be a case where it was necessary. 

"Any time you're releasing personal information you need to be very, very cautious," he told the broadcaster. 

"Is it absolutely necessary for a policing purpose to help achieve the aim of finding a missing woman?

"They've made that call, they've referred themselves to the IOPC. Time will tell whether that was the right call in that circumstance."

Family statement backs police 

A day after police revealed details of Ms Bulley's vulnerabilities, another statement was published on the Lancashire Police website.

It said Ms Bulley's family asked the police force to issue the following statement: 

"It has now been three weeks since Nikki went missing.

"We, as a family, believe that the public focus has become distracted from finding Nikki, and more about speculation and rumours into her private life.

"As a family, we were aware that Lancashire Police, last night, released a statement with some personal details.

"Although we know that Nikki would not have wanted this, there are people out there threatening to sell stories about her.

"This is appalling and needs to stop.

"The police know the truth about Nikki and now the public need to focus on finding her.

"Due to the peri menopause Nikki suffered with significant side effects such as brain fog, restless sleep and was taking [hormone replacement therapy] to help but this was giving her intense headaches.

"The headaches caused Nikki to stop taking the HRT thinking that may have helped her but only ended up causing this crisis.

"The public focus has to be on finding her and not making up wild theories about her personal life.

"Despite what some media outlets are suggesting, we are being updated daily and receive support from our family liaison officers.

"Nikki is such a wonderful daughter, sister, partner and mother and is missed dearly — we all need you back in our lives.

"Nikki, we hope you are reading this and know that we love you so much and your girls want a cuddle.

"We all need you home.

"You can reach out to us, or you can contact MissingPeople.org.

"Don't be scared, we all love you so very much."

Where does this leave the investigation?

We still don't know what happened to Ms Bulley. 

Police said they were throwing an "unprecedented" amount of resources at her case. 

There are dozens of officers and detectives working on the investigation, having looked at hours of CCTV and dashcam footage, interviewing 300 people and sifting through hundreds of pieces of information. 

Search parties focused on the land in the immediate area where Ms Bully's phone was found, a stretch of the River Wyre and the area where the river meets the ocean. 

Here's a series of maps the police published when describing their search efforts:

Based on Wednesday's press conference, it sounded as though search efforts would continue. 

"Water is an inheritably challenging medium to search and the River Wyre is tidal and flows out into the estuary near Crockram Sands," Assistant Chief Constable Lawson said.

"Parts of the river have been searched repeatedly because of the shifting water patterns and tidal nature of it."

But how long will crews keep this up?

"I retain all hope," Assistant Chief Constable Lawson said.

"But the reality is there will be a point at which I need to review, in conjunction with … [Superintendent Smith] and the search managers, the extent and proportionality of continuing to deploy significant search resources around the River Wyre and the land-based options we have there. 

"For this week, the search effort is continuing. 

"There will be a point in the days ahead where I need to review that."