He invented fictional teenagers with fictional backgrounds.

This approach was simpler in some ways — there was no one to compare him against — but also less sustainable, because the fictional background would eventually be checked and found to be fictional.

The Barclay case was distinctive in that it was based on a real missing person.

This created a specific additional risk — the comparison against the real person’s documented characteristics — but it also created a specific additional resource: the credibility that comes from a family’s recognition.

When Carey Gibson said “this is Nicholas,” she was providing a form of validation that no amount of invented fictional biography could provide.