Season 1 of Them premiered on January 1, 2007.

Cain Johnson is the cell's vigilant, determined Enforcer, tasked with investigating agents who "go rogue." A new arrival, he struggles to understand the strange human ways. When cell agent Adam Bridges betrays his own kind because of his love for Donna Shaw—an ordinary human woman—Cain is ordered to hunt him down. Ezekial Smits is the cell's Assimilator, orients new arrivals to this world, then monitors their progress and reports anyone he deems "unstable." The ambitious Tara Spader is in charge of media disinformation; she'll follow any order the silkily domineering Sector Chief Uriah Selleck gives, as long as it assures her advancement within the cell. Naomi Tyler Moore is Tara's counterpart and total opposite, as seductive as she is free-spirited, using her powerful sexuality to gather information on unsuspecting human males.