Strange things happen in Eureka when teenagers begin to build a space jump receiver and the “alien” ship lands in Eureka. Meanwhile, Fargo abandons his car “Tabby” or “Tabitha” who then kidnaps him and Larry (the new owner) to teach them a lesson. To make matters worse, Fargo also has important information regarding the ship to give to Allison. In the end Henry arrives and wipes some of the dust off, revealing the ship to have a US Flag, and thus be of Earthly origin…

Tempers and tensions run high as Eureka hosts long-term rival Area 51 in their bi-annual Eureka-fied bowling tournament. When a series of escalating pranks turns deadly, Carter finds himself chasing down a creation of blob-lical proportions.

A scientist at GD seems to have gone mad as he starts to measure ghosts and spirit, but when things start to fly it’s not a joke anymore. Carter believes it has something to do with the re-opening of section 5, and its new member Tess. Carter and Tess become trapped in the 5th dimension while investigating these strange phenomena.

While Carter is isolated in a D.O.D. recertification test, Deputy Lupo gets to be Acting Sheriff. But she is not acting at all like herself – someone is slowly stealing her identity, Eureka style…

Following Carter’s dismissal, Fargo and General Mansfield decide to field-test a new robotic sheriff named Andy. However, the unfortunate robot seems to be the target of random gravitational anomalies which repeatedly crush him, and Carter cannot help but get involved. After Carter and Andy save the town yet again, Andy realizes that Eureka is better off in Carter’s hands and exploits a loophole in the town charter to have him reinstated. At the end of the episode an alien object is detected heading straight for Eureka.

A doomsday weapon built in the abandoned military complex is discovered, as is the secret Thorne wants to stay hidden – she’s 107 years old, real name Mary Perkins, and was involved in a pre-Eureka research project that developed the first atomic bombs (using radioactive material from meteorites). Meanwhile, Jo and Zane get stuck together, literally, and Zoe’s life is imperiled by the aging syndrome that killed Mary’s colleagues. Allison is found to be pregnant with Nathan’s child. After Jack lets Thorne go, General Mansfield tells Carter that his services are no longer needed by the town of Eureka.

A mysterious “superhero” who can walk through walls and fly is causing a ruckus in Eureka. Meanwhile, Zoe and her friends are trapped in a forgotten bunker that was built before World War II. Zoe slips and falls in a mysterious substance.

Sheriff Carter ends up with an accursed mess on his hands when the opening of an Ancient Egyptian tomb unleashes lethal effects on those who opened it as a swarm of Ancient Bugs are rehydrated (and reanimated). The Bugs use humans as hosts dehydrate and eventually kill them. Once they almost overrun the town, the sheriff and Global Dynamics must contain it or let Eureka fall in to the mercy of a 3000 year old plague.

On Allison and Stark’s wedding day, Sheriff Carter finds himself stuck in a time loop, causing him to experience the same lousy day over and over again. Meanwhile, Sheriff Carter’s sister, Lexi, visits Eureka. As the time distortion escalates and threatens the town and entire universe, Carter’s team takes desperate measures.

It’s time for Eureka’s robotic dog show, and the android canines are out in force. However, when sudden mysterious earthquakes shake Eureka, Sheriff Jack Carter ends up with a pure-bred disaster on his hands.