It is now a month since Samantha Fayet and her baby daughter were swept away in the Asian tsunami.
Samantha Fayet has not been seen since the tsunami
Most of Samantha's family now accept she is probably dead.
But in the latest part of their story, the third in a series, her sister Nathalie Archer tells BBC News she refuses to give up hope she may have survived.
Samantha, 32, was on holiday at the Thai resort of Bang Niang beach in Phang Nga province with her French husband Patrice and their baby, Ruby Rose, when the tsunami struck in the early hours of Boxing Day.
Patrice was injured but survived. Samantha and the baby have not been seen since.
Nathalie, who lives in Barcelona, Spain, said: "I know it's been a month but I've still got that feeling that she's alive somewhere.
"I keep getting told I'm in denial. My family think I'm just hurting myself more by going on believing this.
"But I have to keep on hoping, then if I have to have a big climb-down when the DNA test results arrive then so be it."
As soon as she realised Samantha had been caught up in the tsunami on Boxing Day, Nathalie, 35, flew to Thailand to search for her and Ruby alongside Patrice, who had discharged himself from hospital.
They searched hospitals, scoured lists and looked inside thousands of body bags, until it became clear Patrice was too traumatised to carry on and needed Nathalie to take him home.
She returned on 9 January to continue the search, accompanied by a cousin.
They passed frustrating days visiting villages and showing photographs of their missing relatives in the hope that someone would recognise them.
Six-month-old Ruby Rose was swept from her father into a whirlpool
Once, Nathalie thought they had finally found Samantha, after a man said he recognised her.
She said: "No one spoke English that day so I couldn't understand what they were saying but someone went off in a car and my heart was beating. I really thought we'd found her."
Eventually, it turned out to be a false lead.
They spent four days searching the dense vegetation of the mountainous national park behind the resort, despite the Thai authorities' insistence that no-one lived there.
Although some people had fled to the mountains immediately after the tsunami, local news reports said they had all come back down.
On the fourth day, she says she found signs people had been there.
"I found a British Airways label with a person's name on it, which of course I told the British Embassy about.
"They weren't necessarily signs of people who had just run up there straight after the tsunami.
"There were lots of bandages stuck to trees and plasters with blood on them and a T-shirt with blood on it.
"There were abandoned shoes and polystyrene food boxes. They were things people had taken up there.
"To me, that could be someone who'd been to a refugee camp or a hospital but had been in such a state of shock they just walked away and wandered into the distance."
Nathalie is critical of the Thai authorities, who she does not believe have conducted a thorough search of the mountains.
She says they tried to put her off looking and denied anyone lived there, despite local reports that the mountains were inhabited by Burmese illegal immigrants.
Nathalie thinks her sister could have ended up in the mountains after being swept towards them by the tsunami, or that she could have walked there after leaving a refugee camp or hospital in a traumatised state.
The lush terrain around Bang Niang has proved difficult for searchers
She said: "It's my belief that if there are Burmese people living in the mountains then there could be other people there as well.
"Maybe they are hurt or in shock. Maybe the Burmese are helping them but cannot bring them down because they are afraid for themselves.
But it was impossible for her to search the whole national park on her own.
"It's enormous. To search it properly you would need a large search party and to spend seven or eight days there.
"I know what I'm saying might all sound cuckoo but I still haven't given up hope and I still think something should be done about this."
For now, all she can do is wait and hope. She has told the Foreign Office what she found in the mountains and is waiting for officials to follow up the lead.
Back at home in Barcelona, she said: "I didn't really want to come back but I've got three children and I had to see to them.
"I'm still hoping that somebody might find her up on the mountains somewhere.
"I'm just going to keep my fingers crossed that she's not completely under shock or doesn't want to come back - after all she did see her baby swept away before her eyes.
"I'm still bearing up, because I still have that belief, I still feel pretty strong about it. Though every day it's hard when you wake up and the phone hasn't rung with any news."
You can watch a BBC News Special "Asia One Month On" on this website, BBC1 and BBC World at 1930 GMT.