Cameras have never been. We like to think of it as paradise lost and found. Places teeming with life. Its on land, in the sea. Shark coming in. Could this magical spot hold the secret to help saving the planet . Whats happening is really an sos signal. We have to do something. But first, Richard Engel with an nbc news investigation. The terrorist who grew up next door. Can i talk to you for a minute . When did you learn that hed actually gone to syria to join isis . Right now. You didnt know until right now . Americans who have joined isis. Tonight, we reveal their identities. There are 15 names here. An aspiring doctor, a valedictorian, her husband, their baby, how do these Young Americans become terrorists . Beheadings, the brutality, do you think the boy you grew up with was capable of doing that kind of thing . Yes, in an instant. The exclusive story right now on assignment. Good evening, and welcome to on assignment. Im lester holt. We begin with an nbc news investigation of the e