Madam Ng Mui Chuan, 61, has wandered into the kitchen in the middle of the night to turn on the gas for no reason.
She has strewn rice and oats all over the kitchen, played with her faeces and spent hours on the floor in a foetal position weeping. For no reason at all.
As her dementia advanced, so did her fits of anger and paranoia, says her husband and sole caregiver, Mr Lim Fah Kiong, 68.
When out in public, she would point at strangers and make "scolding noises". Fearful of taking her out or leaving her alone indoors, Mr Lim eventually became a prisoner in his own home.
For the past four years, he has helped his wife eat, dress, shower and go to the toilet. He also cooked, cleaned and did all the other household chores.
He could afford a maid, but chose not to have one. "I was afraid Mui Chuan might hit her. I just can't live with that fear," he says.
When her condition deteriorated late last year, his wife would keep waking him up at night. "I could sleep only one or two hours at a stretch, week after week."
Robbed of sleep for days, there were times he felt he was losing his sanity. He would often break down in tears, he says, but never in front of her.
He knew she had to be in hospital the day she assaulted him with a clothes hanger and tried to smash a fish tank.
He is on the lookout for a subsidised nursing home, but with long waiting lists for dementia patients, the former SingPost executive is bracing himself for round two of his caregiving ordeal.
The couple are childless.
It was not always this way. Mr Lim and Madam Ng retired when they were in their 50s in 2005, eager to spend their golden years with love and laughter - without the stresses of work.
They had married late in life, after meeting at a training course. They planned "makan trips" around the island and to Malaysia.
"We hoped to grow old together as friends and soulmates," said Mr Lim. "Just like when we were young."
But that was not meant to be.
Sitting alone in the study of his spacious and neat five-room flat, decorated with photographs and Valentine's Day cards from his wife, Mr Lim lets on that her problems began innocuously enough.
She would be forgetful and get angry for no reason. She began washing her hands obsessively, every time she saw a tap.
Once a genial, gentle woman, she grew suspicious of even her closest friends. "They hammer me when you're not around," she would tell him.
He took her to a psychiatrist in 2010 after she tried to jump from their eighth-floor flat. She was diagnosed with obsessive compulsive disorder.
He installed window grilles. He soon had no time to tend to his beloved plants and the ornamental fish he kept in a giant double- decker fish tank in his living room.
"My bougainvillea are dead and most of my big fish," he said sadly, as a lone golden dragon fish swam in one of the tanks.
It was only after she was referred to the National Neuroscience Institute in 2011 that she was also diagnosed with Alzheimer's disease - by then already in its moderate stage.
"With so much hype on dementia being an old person's disease, few realise that you can get it even before you hit 50," said Mr Lim.
Despite medicines, the disease continued its inexorable march. By early this year, Madam Ng could not recognise most of her friends and family. He is bracing himself for the time when she forgets him too.
She failed to recognise everyday objects too. When the phone rang, she would put the television remote control to her ear. She left wet slippers on the bed. And once, trying to dress herself, she wore a panty like a shirt.
She went to a day-care centre for dementia patients for one year till early this year, but her frequent "crying, praying and chanting" frightened the other patients.
"I was told I must withdraw her till she gets better," he said. "But she never did."
These days, Mr Lim follows a familiar routine. Every morning, he takes a bus from his Bishan home to the Institute of Mental Health, where his wife is warded, only to return late in the evening.
September has always been a special month for the couple. His birthday is on Sept7 and their wedding anniversary, five days later. They have been married 25 years now.
His wife did not remember either occasion. He spent both days sitting next to her in hospital.
"There is nothing left to celebrate any more," he said.