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.

It's Founder's Day in Eureka and everyone is in the spirit of the celebration until Jack, Allison, Henry, Jo and Fargo are transported back to 1947 where they meet some familiar faces along the way. Will they be able to get back to 2010 or will they be stuck forever in 1947 where Eureka is not a town, but an Army base.

Wormholes randomly materialize around Eureka as the Department of Defense is set to shut the town.

A bad day in the lab forces Carter to rethink his decision to live in Eureka, prompting an intervention from S.A.R.A.H. (the self Activated Residential Automated Habitat.

Ambition trumps common sense when Stark is given a chance to try out the Top-secret artifact. Once it's tested, Eureka warps into the future and ends up in 2010, where the town is different.

The crew moves forward after an ordeal and Warren's visit adds to the pressure.

In the season finale - It's chaos in Eureka when an energy beam rips through main street but the Astraeus launch must go on...with or without Eureka intact.

The Astraeus crew returns to Eureka four years later and must adapt to a myriad of changes, including a more oppressive version of Deputy Andy.

Beverly Barlowe resurfaces in Eureka seeking Carter's help to free the Astraeus crew, and the rescue plan lands Carter in the crew's virtual world.

An unpredictable researcher accidentally unleashes a dangerous artifact which was previously hidden by Nathan Stark.

When the 5 get back to their time, things are changed everywhere. As the Henry tries to fix the machine that transported them in the first place, Dr. Grant is making himself comfortable as he can. Jack is still trying to wrap his mind at the fact that he asked Tess something that she says yes to and the fact that the group's positions changed. As one thing leads to another, a twist happens and things get a little dicey.

Eureka's citizens face the return of people from the past; Global Dynamics tests a new device.

When Grant and Carter become stranded, they must race back in time to save Eureka.

The town huddles in a last attempt to locate the vanished Astraeus before it's too late!

An accident leads a U.S. Marshal and a teenage girl (who later is revealed to be his daughter) to a peculiar town populated by scientists and their families where 10-year-old boys are in 11th grade, the local diner doesn't believe in menus, and E=MC² was just the beginning. Just as the Marshal starts to get settled into the swing of things, a local scientist develops a bomb that seems to appear anywhere and eats all the matter around it.

Something starts to steal the townspeople's memory...

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.

The people of Eureka are being kidnapped and replaced by body-doubles one by one unless Allison, Fargo and Zane can figure out how to avoid capture and save their town.

Strange behavior exhibited by the townspeople is investigated by Carter,who has to solve the mystery before Stark makes a decision that could affect the world.

One of the Global Dynamics tanker trucks spills, potentially causing a change in everyone's sleep habits... In the course of the episode, we come to learn that Global Dynamics has developed a technology that enables them to distill six months of the town waste and by-products into one truck, an amount that would normally fill Lake Erie.

Sheriff Jack Carter becomes absolutely irresistible to every woman in Eureka. But if he doesn't get his mojo under control, they might just eat him alive.

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.

The citizens of Eureka attend the funeral of Susan Perkins, only to find out that she is in fact alive. Meanwhile the Sheriff moves into an underground bunker that is actually a 'smart house' controlled by a computer dubbed 'S.A.R.A.H., and begins to investigate a 'ghost' that has been appearing in town.

After hosting a movie party, Spencer is found the next day in the middle of a crop circle, claiming he was abducted by aliens; and then other people who attended the party start to go missing as well. Elsewhere, the legislator responsible for Eureka's funding visits the town, and gets dragged into a Sector 5 experiment...

A sleeping weapons system is accidentally awakened by Fargo and Spencer. Henry tries to avert the pending catastrophe with the help of a retired, nonsensical scientist.