He could have slipped her the drug, delivered her to be raped by a group, and then left her after his turn. The mother is adamant there are others involved and he knows what happened to her. He doesn't want to tell the truth about what he did but it is possible he does not know her end.
Yes, I think that's a plausible reason they're not getting any leads out of these boys -- because the boys just might not know what happened to her after they left.
An investigator who came on right after Greta seemed to be thinking in that direction too. He said the fact that investigators apparently weren't getting any helpful info out of any of the five boys arrested, after all this time, might be that there was little to get out of them [paraphrased].
That struck me, too...Beth Holloway's insistence that there were others involved in N's disappearance and they'd be brought to justice too. Last night she said she'd been told certain things by authorities, but wouldn't divulge more.