Vulnerable child victims are easy prey to abusers
Vulnerable children plied with drink or drugs and passed between men for sex.
That is what is at the heart of the investigation into the abuse of young people in the care system.
Two years ago a young woman who had lived in care homes across Northern Ireland described her experience to the BBC.
"Mobile phone numbers were passed between girls living in the homes. They would be brought to parties or contacted via Facebook," she said.
Most of the young people at the centre of this current investigation are seen as vulnerable and at risk.
While they have always been part of the social care system, most recently the police have identified a group of 22 children who they believe have been specifically targeted.
Through no fault of their own they become easy prey to certain men who take advantage of them.
While it is an issue that affects all young people, according to health professionals it is those living in care homes who are at particular risk.
In September 2011, the charity Barnardo's produced a report which highlighted that child exploitation was a major problem for the local authorities.
One of the report's authors is expert in child exploitation, Dr Helen Beckett.
"This is horrific abuse that these young people are experiencing, rape, repeated rape, children being beaten and turning up the next day at homes not knowing where they spent the night," she said.
Dr Beckett, who is deputy director of the specialist research centre at the University of Bedfordshire, said the grooming means the children involved become increasingly dependent on the abuser.
"Very often it starts out as good fun. They are being given drink and drugs, then it all takes a sinister twist and they get in too deep. They can't get out of it."
Another issue facing the police is that many of the boys and girls who are targeted are not aware that what is happening to them is wrong.
What appears to be a normal relationship can quickly spiral into a situation where they are being passed between men - including their so-called boyfriend who they do not want to report.
Vivian McConvey, chief executive of Voice of Young People in Care (VOYPIC), said it is an extremely complex situation.
"Part of the problem is that some young people don't see themselves as being exploited. That means it's difficult for the police to engage with them and to identify the perpetrators.
"But this is not a problem for children to solve - it's one for everyone to solve."
According to the police the evidence is shocking - including children being placed in taxis and dispatched to parties. But those in charge say the system has not let youngsters down.
Tony Rodgers from the Health and Social Care Board said those involved in the various agencies have always been working together - but most recently they have stepped up the operation.
"I don't think the system has let the children down. What this demonstrates is a multi-agency approach - all those involved coming together and working together where risks have been identified."
As it is, the police have only scratched the surface of this problem - it is expected that further victims will be identified and arrests made.