Doctors refused to admit a woman to hospital despite branding her a danger to the public hours before she set her flat alight with her mother inside.
Rada Lace had been spotted on the A92 near Carnoustie in the middle of the night on June 3 last year wearing only a dressing gown.
She was taken to Stracathro Hospital in a “catatonic state”, but despite medics saying she was a danger to the public they said they would not admit her.
The police took her to her home in Arbroath and left her in the care of her mother, Anna Lacis.
Ms Lacis told how her daughter had earlier been shouting “unspeakable things” in her car before trying to kick out a window.
Shortly before the fire started, Ms Lacis said, Lace had been “holding something, as if it was a sword.”
She added: “She had wild, sparkling eyes it was non-human. I couldn’t help her, I decided to leave.”
Depute fiscal Joanne Smith told Forfar Sheriff Court: “A short time later the accused’s mother came back into the living room and found the curtains were ablaze.
“The accused was standing outside having a cigarette. The mother suffered facial burns trying to pull the curtains down.
“Fearing she would be overcome by fumes she left and alerted neighbours.
“At 11.54am the Scottish Fire and Rescue Service were called.
“Smoke was seen coming from the ground-floor flat and the accused was pointed out as being responsible.
“She was standing 30 feet away apparently in an almost catatonic state. Five other residents were evacuated by the fire brigade.
“She was later taken back to Stracathro and doctors were of the opinion her mental health hadn’t changed and there was no mental health disorder requiring her to be sectioned.”
Lace, 32, a prisoner at Cornton Vale, pleaded guilty on indictment to a charge of wilful fireraising.
Sheriff Gregor Murray deferred sentence until next month for psychiatric reports and allowed a treatment order on Lace to continue until then.