Here are the main characters on the Sci Fi original series Eureka.
1. Colin Ferguson as Jack Carter
U.S. Marshal Jack Carter drove through Eureka driving his daughter, Zoe, back home from one of her rebellious escapades, but an accident keeps him in town long enough to get to the bottom of an experiment gone wrong that threatened the entire town. His resourcefulness got him the job as the new town sheriff, where he may be scratching his head over the impossible science but when a crisis hits he seldom misses the real clues to the solution. Jack has feelings for Allison and in a destroyed alternate timeline he married her, but Allison's mutual feelings for her ex-husband, Nathan, and her job as head of Global Dynamics have gotten in the way. Jack and Zoe live in an experimental underground house run by an A.I. called S.A.R.A.H.
2. Salli Richardson as Allison Blake
A cool customer who tries to keep her emotions under wraps, Allison started out as the Defense Department liaison to Eureka but replaced her ex-husband, Nathan, as head of Global Dynamics after his obsession with investigating an extra-terrestrial object called the Artifact caused the death of Kim, a scientist who was also Henry's girlfriend. Allison has an autistic son, Kevin, who has special abilities and developed a mysterious relationship with the Artifact. She feels a connection both with Sheriff Carter and with Nathan. (In the first season Salli was credited as Salli Richardson-Whitfield.)
3. Joe Morton as Henry Deacon
Henry is Eureka's all-purpose Mr. Fix-It, a former NASA aerospace expert who spends his time in Eureka tinkering with every conceivable type of device and seems to know how to make just about anything work. His hobby is fixing cars, so he operates out of Henry's Garage, but his interests range far beyond ordinary engines. Henry is close friends with Sheriff Carter, who turns to him when the science needs explaining (he has a knack for putting things in layman's terms). But Henry keeps secrets even from Jack. He created a false timeline in order to save Kim from dying while investigating the Artifact, and when Jack was sent back in time to stop Henry, Henry was forced to accept Kim's death but wiped Jack's memory of the alternate future.
4. Jordan Hinson as Zoe Carter
Zoe is Sheriff Carter's irrepressible daughter. In the past prone to acting out her frustration with her parents' divorce (caused in part by Jack's dedication to his work as a marshal, which his wife and daughter tended to think he chose over them) with acts of petty crime, Zoe has increasingly found a home in Eureka even as their stay together in the town has helped Jack relate to his daughter better and become a more attentive father. Zoe's concern then became fitting in as a normal girl in a town full of genius's kids, but she eventually found she was smarter than she thought -- though she hid her IQ results from her dad to keep him from thinking too bad about himself.
5. Erica Cerra as Deputy Jo Lupo
Jo is Sheriff Carter's gung-ho deputy, a weapons expert with advanced army training who chafes a little at her second-in-command role, though she seems to recognize that someone needs to be in charge whose first impulse isn't to shoot things. She presents a hard edge but is capable of being more feminine and vulnerable, particularly around newcomer Zane. At one point she also showed some affinity with fellow artillery fiend Taggart, despite the age difference. Jo made friends with Zoe and sometimes talks girl-talk (and Jack talk) with her.
6. Ed Quinn as Nathan Stark
Nathan was the head of Global Dynamics for the first two seasons and therefore in some ways the most important man in Eureka. Cocky, handsome, and brilliant, with a Nobel Prize in physics behind him, Nathan became fixated on attempting to understand an extraterrestrial object called the Artifact. When his experiments led to Kim's death he was replaced by Allison, his ex-wife, but she convinced him to stay on in Eureka. He has a mutual antipathy with Sheriff Carter, but they've worked together in a succession of crises and have a grudging respect for each others' abilities, though they are also rivals for Allison's affections.
7. Neil Grayston as Douglas Fargo
Fargo is an accomplished scientist himself but his tendency to bungle whatever projects come his way have left him in the role of executive assistant to the head of Global Dynamics. Fargo comes across as a typical geek, fantasizing about the town's beautiful and unattainable women and prone to expressing the negative side of things, event to the point of being ungrateful. He's aware of his reputation as a screw-up and tends to overcompensate for it. His self-confidence received a boost when it was discovered that credit for several of the town's early revolutionary discoveries was stolen from his own grandfather.
8. Matt Frewer as Jim Taggart
Taggart is Eureka's animal expert. Off-kilter and with a jaw-bending Australian accent, Taggart often takes his huntsman's obsession with woodland creatures a bit too far. He's also quite familiar with science and technology, once building a flock of animatronic geese in order to study migration patterns. His wild-eyed, unpredictable behavior can cause others to be leery of him, but he has a soft spot for Jo as a fellow red-blooded action-type in a town full of eggheads.
9. Frances Fisher as Eva Thorne
Eva Thorne arrives in Eureka at the start of season 3 with a notorious reputation, a moniker — "The Fixer" — and unlimited power over the town, its citizens and Global Dynamics. How she uses that power, and to what ends, is sure to have an impact on everyone in Eureka. Her arrival is triggered by the events at the end of season 2, in which a metal-eating bacteria strain caused extensive damage to the town.
10. Niall Matter as Zane Donovan
Zane arrived in town with a reputation both as a troublemaker -- he was wanted for a string of high-tech crimes -- and as one of the most gifted technosavants of his generation. Initially mistrusted by Sheriff Carter, Zane soon revealed his good intentions even if his swagger remained intensely irritating. When Eva Thorne finds him, she realizes that his astonishing intelligence may prove useful. How far Zane will go to please Global Dynamics' new boss remains to be seen.