Sudden muteness, human bioluminescence and faucets running blood cause many of Eureka’s citizens to believe that they are the victims of a biblical plague.

Dr. Whiticus creates an incredible "weather machine" intended to reverse the effects of global warming which instead stirs unexpected results.

Carter's romantic surprise for Allison turns deadly when they're trapped in a sinking marine lab with time and oxygen quickly running out.

Global Dynamics sonic cleaning coincides with a phenomenon in which the citizens of Eureka develop a form of amnesia. Meanwhile, Allison goes into labor.

The quaint town of geniuses is transformed into animated versions of themselves. Sheriff Carter and Allison Blake are secretly planning the perfect holiday surprise for their kids. But a mysterious kaleidoscopic wave of color crashes over Eureka, leaving the entire town and its inhabitants animated.

A former resident returns to Eureka and creates mayhem which threatens Global Dynamics, prompting Stark to take action.

Taggart achieves a medical breakthrough while Fargo invents a device that bridges the divide between computers and human brains.

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.

Carter investigates an unusual car accident. Meanwhile, Stark, under the stress of completing a project on time, pressures two research teams to produce results.

Falling space debris threatens Eureka residents and Carter turns to high school science fair participants to solve the problem. Specifically, he taps a student science project created to harness the sun's energy. Also, Zoe gets an eco-friendly automobile.

Beverly Barlow returns to town just as a parasitic bacterium threatens to destroy Eureka, by turning everything to gold and then into rust --- people included.

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

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.

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

It's space week in Eureka, and everyone is gearing up for the rocket race - except for Carter. General Mansfield is in town for the big Race to the Moon, and is debriefed on a new oxygen-generating fluid designed, called TAP, for colonizing Mars. When the question about someone using TAP to fuel their rocket, the whole town of Eureka is in danger and it is up to Kevin to save the day this time. Will he do it, or will Jack come back to see charred remains of his friends?

Carter can't get into the Christmas spirit especially with the town surrounded by a force-field. Fargo organizes the GD holiday party, and Allison is full of holiday cheer.

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.

Jo displays atypical behavior after a DNA scan malfunctions, unfortunately it's while she's interim sheriff because Carter is undergoing a 48-hour DOD recertification test.

The Eureka atmosphere becomes toxic when Department of Defense auditor comes to assess the team's relationships.

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.

Taggart's theory is that solar flares caused by the eclipse, or the 'Phoenix Effect', are to blame when people start to spontaneously combust. When Carter discovers that a blast of radiation from the artifact had penetrated the wall of the chamber and is actually to blame for the spontaneous combustion, it becomes a race against time to save the other two people exposed - Nathan and Kevin!

Fargo accidentally triggers a prototype for a personal force field, which goes out of control, forcing Carter to enlist Stark's help.

Carter suffers a blow to the head, and after arguing with Zoe, he suddenly finds himself in a parallel Eureka, where the residents seem to be mysteriously vanishing.