The search is one for an escaped drone as Eva Thorne arrives to assist the clean up of damages which Global Dynamics has caused.

Carter and Allison investigate when a scientist mysteriously disappears from a sealed biosphere. Meanwhile, the Fixer tries to make Eureka's efforts more profitable.

Eureka's annual dog show is underway and is like none other. Meanwhile, Sheriff Carter experiences an earthquake; Zoe debates quitting the accelerated physics program; and Allison starts the process of fitting her wedding dress.

It's Allison and Stark's wedding day and Carter finds himself reliving it over and over. Meanwhile, Carter's sister, Lexi, visits the town.

A search for a mummy ensues after a famed archaeologist opens the tomb of an Egyptian queen at Global Dynamics.

Carter's job is made more difficult when a super hero emerges. Meanwhile, Zoe and her friends are imperiled when Thorne makes a subterranean search beneath Eureka.

The Eureka mayoral race is overshadowed by the sudden arrival of a second sun, forcing Carter, Allison and Zane to investigate it more closely.

Trust issues are produced by a scientific find, along with sinister results. Zoe's life is in jeopardy, and Eva Thorne knows what has caused the predicament.

Carter interviews for a job with the Department of Homeland Security, after being terminated as the sheriff. Deputy Lupo decides to resign after discovering that a very personable robot is the new sheriff.

Carter’s recertification exam tests both his body and mind. Allison explains the new town wide DNA-monitoring security system to Henry which leaves Deputy Lupo injured during its initial scan.

Dr. Tess Fontana reopens Section 5, causing objects to become ambulatory , possibly due to poltergeists.

Carter finds himself chasing down creation of blob-ical like proportions when a series of escalating pranks turn deadly. Elsewhere, long-term rivals from Area 51 come to Eureka for a bowling tournament.

Eureka’s teenagers who appear to have been manipulated while asleep, gathered in a field where they assembled a strange structure comprised of scrap metal and electronics.

Henry’s ship returns causing Carter to fear it maybe linked to the town’s deadly electrical anomalies.

Allison’s baby shower fetches her a load of eco-friendly gifts and the discovery of a drowned scientist in a location where drowning is impossible.

Global Dynamics sonic cleaning coincides with a phenomenon in which the citizens of Eureka develop a communal form of Alzheimer’s disease. Meanwhile, Allison goes into labor.

The first day on the job as temporary head of Global Dynamics proves daunting for Tess when a new Ice Age comes to Eureka; and a familiar face returns in the process.

Tess has a job offer from Australia, Zoe is prepared to leave for Harvard and Carter has a magnetic disturbance above Eureka to contend with, in the third season finale.