Aptly named drama The Affair has completed its main casting with Monday’s announcement that Joshua Jackson has signed on. Based on Long Island, the Showtime original centers around the infidelity between Allison (Ruth Wilson) “a young woman, working in a pancake house, trying to piece her life back together in the wake of a tragedy,†and hot shot New Yorker Noah (Dominic West). Maura Tierney will play Helen, “Noah’s college sweetheart, best friend, mother of his children, lover and wife of 17 years, whose world will be buffeted by Noah’s infidelity and who, over time, will swing back and forth from understanding to furious, and from forgiving to vengeful,†while Jackson (fresh off his five years on Fringe) will fill the role of Cole, “a hard-edged cowboy who manages a ranch on the eastern tip of Long Island that has been in his family for generations.†Jackson as a hard-edged Long Island cowboy seems a bit far-fetched, but then so is the idea that anyone would ever cheat on Pacey Witter.