FBI Agent Audrey Parker was assigned to Haven, Maine to bring back an escaped convict named Jonas Lester. Audrey thought this was a routine case, while we saw her supervisor, Agent Howard, clearly sent her there for a deeper purpose.
Audrey realized Haven was unlike any other town when she learned Lester died at the hands of weather controlled by Marion Caldwell. Haven was plagued by "The Troubles" - powers and abilities possessed by residents that often caused chaos and destruction.
Audrey received a shock when local newspapermen Vince and Dave Teagues presented a Haven newspaper clipping from 1983, about the unsolved murder of someone known as "The Colorado Kid." In the photo was a woman, Lucy Ripley, who looked EXACTLY like Audrey.
With no knowledge of her real parents (She was raised in foster care), Audrey decided to stay in Haven for a few weeks to investigate the woman in the Colorado Kid photo. She called Agent Howard and let him know she was taking vacation time - but we saw that Howard was actually in Haven, watching her. Hmm...
Audrey learned Nathan was "Troubled" - he couldn't physically feel anything. Except for her. Audrey (and everyone else) realized she was immune to "The Troubles." The fact that Nathan could actually feel something with her upped the attraction between them.
Big Dramz happened when Nathan's dad, Chief Wuornos, revealed Nathan was adopted AND outed himself as "troubled" (he could cause cracks in the Earth). The Chief's power got the best of him, and he ended up turning to stone. Which left Nathan as the new Chief.
Audrey resigned from the FBI and accepted a job with the Haven PD (and we saw Agent Howard was secretly pleased). Audrey believed she WAS Lucy Ripley, due to a scar on her foot that both women have/had. She was determined to figure out what the hell was going on (and why she didn't age).