The husband of missing woman Tina Satchwell says he believes she received "a helping hand" in her disappearance.
Mrs Satchwell (45) disappeared last March from her home in Youghal, Co Cork.
Gardaí have since followed up hundreds of leads and potential sightings across Ireland, the UK and beyond, but to no avail.
Speaking on 'Prime Time', her husband Richard said he believes somebody knows where she is.
Appealing for his wife to make contact if she can, Richard told the programme it "dawned on him" recently that Tina may have planned to leave, but he does not believe she could have done so on her own. "As far as I'm concerned, my wife is out there and she'll come back. I truly believe that.
"She didn't get up and leave without some kind of help from somebody."
Describing his wife's demeanour in the months before she went missing, Richard said she was concerned about a problem he did not wish to disclose to the public.
"She obviously felt she needed a break, to get her thoughts together, to get her head straight," he said.
"She could be there laughing and joking one minute, and the next she'd be crying, just like a switch."
He added: "It's lonely because I built my life around her. And when that's gone, you've nothing."
Mrs Satchwell is understood to have left the house with two suitcases and more than €26,000 in cash on March 20, 2017.
Richard said he returned from a four-hour trip to Dungarvan to find her keys and mobile phone in the house, but she had disappeared.
He said he initially believed she had travelled to stay with family, but raised the alarm four days later when family members in nearby Fermoy said they had not heard anything.
Sarah, a cousin of Mrs Satchwell from Fermoy, said her disappearance is a "complete mystery".
"It tears us apart not knowing. Every day you get a missed call on your phone or you're checking the newspaper, the radio, anything for a bit of news."
"Someone has to know something, no one can disappear without anyone knowing."
Gardaí told the programme they have followed up numerous possible sightings throughout Ireland, the UK and further afield, but all yielded negative results. They said they have harvested hours of CCTV footage and checked all the ferry ports and airports to establish if she left the jurisdiction. They also noted that an obstacle to the probe is the lack of CCTV footage available in Youghal.