Lost The Astraeus crew returns to Eureka four years later and must adapt to myriad changes, including a more oppressive version of Deputy Andy.
The Real Thing Carter and Andy are jailed for trying to steal a piece of equipment to complete a device that Kevin has assembled to search for the Astraeus crew. Meanwhile, Holly comes up with a dangerous theory.
Force Quit 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.
Friendly Fire Fargo deals with Holly's death; Zane and Allison evaluate their romantic relationships after their experiences in the virtual reality; a project threatens to ignite the town.
Jack Of All Trades DOD psychological assessor Warren Hughes resurfaces, and Carter begins to exhibit strange behavior.
Worst Case Scenario A disaster-preparedness drill for Global Dynamics goes awry and imperils the town. Meanwhile, Zane participates in a secret simulation for Fargo.
Ex-Machina Fargo thinks Holly is alive in the virtual Eureka, but a security program hampers efforts to retrieve her consciousness. Meanwhile, Carter is linked to seemingly paranormal activity at Global Dynamics.
In Too Deep A submarine mishap ruins a romantic outing for Carter and Allison, and Jo must sort through pranks at Global Dynamics to save them.
Smarter Carter Allison's brother visits to meet her new husband; Carter's intelligence mysteriously begins to grow exponentially.
The Honeymooners Carter's honeymoon with Allison is complicated by saboteurs in Eureka.