One morning, Katherine Waxman looked at her husband, Sheldon, and asked him who he was.
She had been battling mental illness for almost a decade, but this was new.
He told her his name, and she eyed him incredulously.
"No, Sheldon's a good guy," she told him. "You're hateful. You're a terrible person."
Ms. Waxman, 55, suffers from Capgras delusion, which can accompany schizophrenia and causes individuals to believe their loved ones have been replaced by imposters.
In Canada, doctors see only about 50 to 100 cases a year, but the disorder has entered the public consciousness of late with the trial of Tony Rosato, a former SCTV cast member who is facing charges of criminal harassment against his wife. According to his lawyers, Mr. Rosato suffers from Capgras and believes his wife and daughter have been substituted by mysterious twins.
It is the stuff of science fiction, a bizarre affliction that has formed the plot of CSI episodes and the 2006 novel The Echo Maker. It is even referenced in the new film The Invasion, a remake of Invasion of the Body Snatchers that will be released tomorrow.
But for the family members of those who suffer from Capgras, the strange delusion is all too real.
They must struggle to deal with wives, husbands and children who suddenly look at them as strangers, and often perceive them as a threat.
"It's hard on the families," said Joel Jeffries, a psychiatrist at the Centre for Addiction and Mental Health in Toronto who has seen several cases of Capgras. "You explain that it's part of the illness and not to take it too personally, but it is personal because they're seen as the imposters."
Mr. Waxman said it has been torture to slowly lose his wife of 31 years, but he has grown immune to her accusations."I'm numb to it now," said the 66-year-old lawyer who lives in Grand Rapids, Mich. "I've developed a thick skin."
He met Ms. Waxman when she was working as an intensive care nurse. She was so full of energy that he used to call her "the butterfly" because she was constantly flitting from one place to the next.
"I left my first wife to marry her," he recalled this week. "She was the woman of my dreams."
But 15 years into their marriage, she began to change.
She became despondent and suffered what doctors classified as a "psychotic break," usually the first episode of a decline into schizophrenia. She was given tranquillizers, hospitalized repeatedly and eventually diagnosed with schizoaffective disorder, which combines the psychotic symptoms of a thought disorder with the manic components of a mood disorder.
She heard voices, carried on conversations with invisible characters and paced the yard of their home screaming to the sky.
"It was horrible," her husband said.
The Capgras delusion came later, he added, and was always directed solely at him.
Some sufferers, perhaps including Mr. Rosato, believe that several people in their lives have been replaced by strangers. Others suffer "mirror self-misidentification" in which they believe their own reflection is an imposter.
In his book Phantom s in the Brain, California psychiatrist V.S. Ramachandran describes a Capgras patient who thought his poodle had been replaced, and another who woke up each morning believing his shoes had been switched in the night.
Ms. Waxman recognizes her children, who are 30 and 26, but is constantly suspicious of her husband.
"If I'm not Sheldon, how come your children accept me as being Sheldon?" Mr. Waxman used to ask his wife. "She would tell me I had them brainwashed."
