I go back and forth between a few different theories as to what it could possibly be. For me, however, human trafficking is not likely, and neither is anything drug-related (e.g, that Danielle was a confidential informant, a deal gone wrong, etc. - I am of the opinion that the DEA's role in the investigation is limited to its computer forensics program and laboratory system, and the same goes for the Secret Service; more on these agencies' investigative capabilities at below links). Whatever it may be -and I may be totally off-base here-, I just have this nagging feeling it's going to be something completely unexpected, or a surprise. And it should remain that way, as long as LE needs it to.
https://www.dea.gov/ops/cfp.shtml (DEA's Computer Forensics Program)
https://www.dea.gov/ops/laboratories.shtml (DEA Laboratory System)
https://www.secretservice.gov/investigation/#forensic (Secret Service's Forensic Services)
http://www.slate.com/articles/news_...e_usually_involved_in_molestation_cases_.html ("What Do Counterfeiters, Assassins, and Child Molesters Have in Common? They're all investigated by the U.S. Secret Service.")
