Season 3 kicks off with a hunt for an on the loose drone while Samantha Thorne (Frances Fisher) makes it on the scene to supervise the clean-up of wrongs caused by Global Dynamics. City is threatened by an intelligent drone with "issues" after an anti-missile test. Meanwhile, Eva Thorne, dubbed "The Fixer" after dismantling and rebuilding several corporations, arrives in Eureka to assess Global Dynamics' expenditures.

A scientist somehow vanishes from a sealed biosphere. Sheriff Carter and Allison investigate the disappearance of a scientist from the biosphere. Meanwhile, the "Fixer" endeavors to attain Eureka's attempts to make it profitable. Meanwhile, Thorne continues to apply her business attitude to the running of Eureka.

It's time for Eureka's robotic dog show, and the humanoid canines are out in force. However, when unexpected mysterious earthquakes shake Eureka, Sheriff Jack Carter could end up with a pure-bred catastrophe on his hands. Meanwhile Zoe concerns about the impact of the accelerated physics program on her life.

The reaching of Allison and Nathan's conjoining day concurs with an apparent loop in time, and Sheriff Jack Carter is bewildered that he and only he is re-experiencing Allison's wedding day over an once again. Carter also gets an unforeseen extended visit from his free-spirited sister Lexi. By episode's end, one of Eureka's champions will fall.

Sheriff Carter finishes up with an accurst mess on his hands when the opening of an Ancient Egyptian tomb lets loose lethal effects on those who opened it as a cloud of Ancient Bugs are rehydrated (and recreated) . The Bugs use humans as hosts dry up and eventually kill them. Once they almost overrun the town, will the sheriff and Global Dynamics be able to arrest it or will Eureka fall in to the clemency of a 3000 year old plague?

Zoe and her friends are threatened when Thorne arrives at a subterraneous research at a lower place in Eureka. Carters' job becomes more of like a pain in the ass as a superhero comes to the town. It can move through the walls of the town and hence creating ruckus all around the place. It demands immediate check.

The arrival of a second sunlight meaning presence of a second sun over Eureka totally upstages the town's mayoral race. The presence of the second sun forces Carter, Allison and Zane to investigate the fiery threat endangering the town. The town is in danger and requires the immediate attention of these people

This installment will be the mid-season closing curtain and the final sequence to be broadcast in the year of 2008. A technological finding brings about certain forbidding results creating trust issues; Zoe's life sentence is threatened, and Eva Thorne recognizes that the generator of the predicament.

After being terminated as the sheriff, Carter questions for a job with the Department of Homeland Security. Deputy Lupo chooses to resign after discovering that the very personable new sheriff is a robot. As Eureka's residents prepare for Carter's departure, he takes it upon himself to investigate sudden cases of vivid gravity popping up all over township.

Deputy Lupo stands in as the acting sheriff while Carter undergoes his annual physical, but she's not acting like herself. Carters recertification exam essays both his body as well as mind. Allison excuses the new township wide DNA-monitoring security measures to Henry which allows for Deputy Lupo bruised during its first scan.

Fontana (Jaime Ray Newman) shakes things up in Carters world when shes brought in by Allison to re-open Section Five. Objects become ambulatory after Dr. Fontana reopens Section 5, which may be the work of poltergeists. She shakes things up in Carters world when shes brought in by Allison to re-open fifth section.

Carter chances himself chasing down after the existence of number of blob-ical like proportionality's when a series of intensifying antics turn very insanely. Elsewhere, long-term challengers from Area 51 come to Eureka for a bowling tournament and challenge them. Carter ther probes an intensifying series of pranks.

Teenagers construct an odd building in a Eureka field while asleep. The members of Eureka are horror-stricken by the appearing of an cryptic Stonehenge-looking body structure constructed out of scrap and stolen electronics, and Carter comes across that the edifice was constructed by teenagers under mind control.

Henry's ship returns back to the eurekan township and Carter believes that it may be associated to the township's deadly electric anomalousnesses. Even though the ship was built in a pretty clean-room, even then a "DNA cell" of Dr. Kim made from a very well-matched match and grew to the same human form.

Allisons child rain showers brings in her a large consignment of the various eco-friendly givings and the breakthrough of a drowned scientist in a positioning where drowning is practically very much out of the question. Baby gifts for Allison's shower tests the boundaries of eco-friendly blueprint.

It's a meddlesome day for Global Dynamics and Eureka as Allison's labor commences during a sonic cleansing of the company, and the townsfolk exhibit Alzheimer's disease at the same fourth dimension. The town experiences memory loss while Tess is recording a databank of the inhabitants' recollections.

The beginning of the very first day on the job as the temporary head and manager of the Eurekan's Global Dynamics proves a very highly daunting task for Tess whilst a new Ice Age starts upon in the environment of Eureka. Also an acquainted face returns in the process of beginning of the ice age.

In the third season ultimate finale, Tess picks up a very good job offer in the Commonwealth of Australia, the land of the kangaroos and emus, Whereas Zoe is determined to leave for Harvard for higher education and Carter will have to contend with a hovering magnetic disturbance that's being adrift above Eureka.