The 60th anniversary of Eureka becomes life-changing in more ways than one when a marriage proposal is eclipsed by a mysterious transport to a military site and a new face in the crowd.

When the group gets back to present day Eureka, they discover that normal just left town.

Dr. Isaac Parrish, the brilliant director of the Non-lethal Weapons Lab, is feeling a little undervalued these days. Then all his latent hostility goes viral, infecting everyone with such fury that no one is safe, especially Fargo.

As Eureka celebrates Space Week, Dr. Ramsey unveils his cutting edge invention that could allow colonization of Mars. Unfortunately, a slight malfunction may cause it to incinerate Eureka before the dream is realized. Equally bad is that Eureka's go-to guy for crisis intervention has just gone to Boston to visit his daughter at Harvard.

Claudia Donovan visits Eureka to see if Fargo's promises of wondrous devices are true, but she finds herself in the middle of a mystery suitable for Warehouse 13 when objects begin to appear randomly around the town and GD, and it must be solved before there are deadly consequences.

When Sara gives Andy a (as Zane calls it ) an EMO download to give him emotion, she inadvertently affects all Level 6 AIs. Including Tiny. She escapes while being transported to NASA and is on the loose. Meanwhile, Jack takes Kevin camping with Fargo and Grant and Jack is not happy that Grant is there. They argue on who is with Allison and who is not and they are interrupted by Tiny who has an attachment to a certain object of Kevin's.

The rivalry between Carter and Grant for Allison reaches a new -and dangerous- level.

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.

Carter's plans to visit family for the holidays are thwarted when the town is trapped by a electromagnetic shield.

Carter lands in an awkward situation after S.A.R.A.H. and Andy's nuptials hit a snag; Zane keeps harassing Jo for details; an unscheduled launch presents trouble for the gang.

Fargo demonstrates the FTL device and Holly disappears causing a stir.

Jo receives a technical boost to her crime-fighting ability with lenses that predict security breaches. Allison's headaches won't go away so Carter plans a vacation. Fargo, meanwhile, deals with an onslaught of volunteers when he announces a space mission with room for civilians.

Carter must solve a bank robbery before the town floats away; Allison struggles with episodes of lost time.

Jo and Zoe return to Eureka only to find the entire town incapacitated and communications cut off.

Robotic bugs plague Global Dynamics, and Carter talks to Allison about her mental state.

Jo has wedding ideas for Henry and Grace; the Department of Defense sends a relationship auditor to assess Carter and Allison; Tiny's return threatens the town with poisonous gases.

The Astraeus mission is in jeopardy when a bizarre attacks start occurring around Eureka.

Carter and Taggart probe the mystery of a melted cow; Jo questions what she wants from life; a malfunction strands Deputy Andy on Titan; Carter and Allison contemplate what's next for their relationship.

In the Season 4 finale, Carter and Jo respond to a mysterious attack on the presidential convoy; good-byes are exchanged before the Astraeus mission is launched; and cosmic anomalies threaten Eureka.