Dennis Ryland
Dennis Ryland (Peter Coyote) was the original supervisor of NTAC, the federal agency created to investigate and oversee The 4400. Dennis was promoted to deputy director of NTAC and moved to Washington, D.C., leaving Nina Jarvis in charge. He soon returned, though, to oversee the investigation of the disease afflicting The 4400.

But it was later revealed that Ryland was, in fact, the mastermind behind The 4400's illnesses. His experiments aimed to control The 4400's abilities by inhibiting the production of promicin. He was arrested after his involvement was uncovered by Tom Baldwin and Diana Skouris.

Diana Skouris

Диана Скорис/Diana Skouris (Жаклин Макензи/Jacqueline McKenzie) является ведущим агентом NTAC, и наряду с партнером Томом Болдуином/ Tom Baldwin, была в центре расследования 4400. Благодаря своей работе с Томом она способствовала раскрытию экспериментов ингибитора промицина.
Хотя она и была предусмотрительной по отношению к 4400, Диана сформировала связь с похищенной Майей Рутледж/Maia Rutledge. Не имея собственных детей, Диана вскоре удочерила Маю. Теперь, привыкая к новой жизни в виде родителя, Диана должна держать равновесие между целями ее работы в NTAC, и выращиванием собственной 4400.

Она в настоящее время находится в начальной стадии отношений с "мозгом" NTAC Марко Пачелла/Marco Pacella.

Marco Pacella

Марко Пачелла/Marco Pacella (Ричард Кахан/Richard Kahan) является главным мозгом теоретической комнаты в NTAC. Марко помогает Тому Болдуину/Tom Baldwin, и Диане Скорис/Diana Skouris найти смысл в бесчисленных волновых эффектах, вызванных 4400. Марко недавно наладил отношения с коллегой в NTAC Дианой.

Nina Jarvis

Нина Джарвис/Nina Jarvis (Саманта Феррис/Samantha Ferris) является главой Тихоокеанского Северо-западного Подразделения NTAC, заменяющая Денниса Райланда/Dennis Ryland. Хотя будучи на больничном от NTAC, из-за ранения, Джарвис скоро вернулась в команду и с неё были сняты все подозрения по поводу причастности к скандалу ингибитора промицина.

Tom Baldwin
Tom Baldwin (Joel Gretsch), together with his partner Diana Skouris, is one of the lead NTAC agents responsible for investigating The 4400.

Although committed to working with NTAC to discover the truth about The 4400 and avoid the predicted catastrophe, Tom can't help being affected personally by The 4400. His nephew Shawn, who was abducted, now runs the very center he's investigating, but more significantly, his son Kyle emerged from a three-year coma with a deep secret. While possessed, Kyle murdered Jordan Collier. Kyle confessed to the murder, allowing Tom to expose Dennis Ryland's inhibitor scandal, but the damage had already been done. With his family now is shambles, Tom must sit by as his son awaits trial.

Fortunately Tom has found a place of solace during these trying times. A 4400 who Tom fell in love with, Alana Mareva has the ability to create comforting alternate realities for her and Tom. It was in one of these realities that they fell in love and married.

As Tom proceeds with his work at NTAC, he must balance the effects the 4400 have had on him personally and professionally. Who, in these confusing times, does he side with?