Sheriff Jack Carter (Colin Ferguson) is a U.S. Marshal who reluctantly ends up as Sheriff of Eureka. Jack is consistently dumbfounded by the wonders Eureka produces, as well as their propensity to produce things that often threaten the entire town, if not the world. Despite being an average man in a town full of geniuses, Jack's admittedly simplistic ideas and ability to make intuitive connections between seemingly disparate events often save the day. (This is in contrast to the other residents of Eureka, who, being stereotypical scientists, tend to over-complicate things and get lost in minutiae). Jack has deep feelings for Dr. Allison Blake, although his reaction to new arrival Dr. Tess Fontana result in a blossoming relationship. However, by the end of Season 3, the situation once again changes and at the end of the season finale, we find Carter at a crossroads with an important decision to make which could impact upon his relationships with both Blake and Fontana...