One in six councils is failing to protect vulnerable adults in their care, the BBC has discovered. File on 4 uncovered this disturbing story.
Suffering a severe form of autism means the welfare of James, 39, is always a concern for his family.
They say his condition makes him particularly suggestible and easy prey for others.
But the normal worries of his sister Linda were heightened a year and a half ago when she began to suspect somebody was stealing from James, who was living in sheltered accommodation with no support from staff overnight.
He told his sister another resident was taking items from his bedroom and entering without his permission and had taken money from his trousers while he was still wearing them.
His family believe an estimated £2,000 was stolen over time but worse was to come.
Linda was shocked when James's behaviour in the shower one day seemed to indicate he had suffered sexual abuse and even rape.
"He started crying and I'd never seen him crying. He said this other person keeps hurting me," she told BBC File On 4.
"It was very distressing."
Another sister witnessed the same behaviour and the family's fears increased when his daily care worker said that James told her another resident had been in the shower with him.
The care worker told the family and her bosses about the concerns.
His family are still seething at the "professionals meeting" called by Halton Borough Council which they say was riddled with inaccuracies.
"We thought it was disgusting, they didn't even get his name correct...it said there was no evidence of a change in his relationships but staff remarked how unresponsive he was and had not been out of his room for days," said Linda.
An independent council report said the notes of the meeting were very poor.
It criticised the fact that neither the police nor several health professionals were present at what should have been a multi-agency meeting.
The care worker who knew him best was not invited to attend.
The council director of social services told the family that after a police investigation the Crown Prosecution Service (CPS) found there was insufficient evidence to take the case further.
Yet when contacted the CPS said no such case had been referred to it.
The independent report "largely upheld" the family's complaints but Linda said the council's response has been inadequate.
"There was no personal apology to James and no recognition of the hurt caused by failing to take proper steps to protect him," she said.
Halton Council said it is working with its legal advisers and the family to "resolve this matter as soon as possible."
The council added: "At this stage it would be inappropriate to comment any further."
Hear the full story on Radio 4: File on 4 Tuesday, 20 March, 2007 at 2000 GMT.