An ambulance crew put an 89-year-old woman to bed in the wrong house after she was discharged from hospital, her son has said.
Elizabeth Mahoney had been in County Hospital in Pontypool, Torfaen, for 10 weeks being treated for Covid-19.
But when she was discharged on 12 March, instead of being taken home, Ms Mahoney's son Brian said she was taken to a stranger's house in Newport.
The Welsh Ambulance Service said it had apologised to the family.
Mr Mahoney said his wife went to meet his mum at her home in Pontypool on the day she was due to be discharged because he had a cold.
But when there was no sign of her, Mr Mahoney called the hospital to see where she was and was told the ward manager would call him back because there had been "a bit of an issue".
More than two hours later, he said, he was told she had been taken to Newport.
Mr Mahoney said he assumed she was still in the care of the ambulance crew at this point, so was shocked when he received another call from the ambulance service later to say "we are on our way to pick your mum up".
"I said 'what do you mean you are on your way to pick mum up?'," Mr Mahoney recalled.
"And he said 'well, we have left your mother at a house in Newport', which we couldn't believe."
Mr Mahoney said he understood his mother had tried telling the crew she was not the patient they thought she was, and that she was being left at the wrong house.
"Mum was frightened then because she thought we were putting her in a home," he explained.
"I don't know what she thought really. They left here there for over two hours."
Mr Mahoney said they had learned from the ambulance service that his mother had been put to bed in the mystery house.
He added that he had been told the man who lived there had been expecting the arrival of his sister, who had dementia, but had not immediately realised Mrs Mahoney was not his sister.
Mr Mahoney said his mother was a "good mum" who had been through a lot.
"My dad had dementia for a good number of years," he said.
"Dad passed away two years ago. After six months of dad having dementia, mum had a stroke. And she went on to break her hip, so she's been through a lot over the years.
"Mum's [health is] bad enough as it is... so this certainly hasn't helped."
Mr Mahoney said he did not want to see anyone punished for what had happened, he just wanted to see measures put in place to stop what happened to his mother happening again.
"We have all supported the NHS, but we just feel something should be in place to make sure nothing like this happens again to anyone else," he said.
Mark Harris, of the Welsh Ambulance Service, confirmed a patient had "regrettably" been "discharged to the wrong address for a short period of time".
"We are working closely with colleagues at Aneurin Bevan University Health Board to fully understand the chain of events and establish exactly what happened," he said.
"We have extended a sincere apology to both families concerned for the distress caused and will continue to liaise directly with those families as the investigation progresses."
In a statement, Aneurin Bevan health board said: "We acknowledge the upset and distress this incident has caused Mrs Mahoney and her family and we are co-operating with the investigation being undertaken by the Welsh Ambulance Service."