It's Allison's wedding day, and Carter is stuck in a time loop that causes him to relive it over and over. Unfortunately, there's no simple act that will right things, and the solution may prove very costly.
Wormholes cause trouble on moving day. Or is moving day causing trouble with wormholes? While Jack tries to fix the wormholes Fargo is determined to something about moving day.
During the Founder's Day celebration, Jack, Allison, Fargo, Henry, and Jo somehow end up in 1947, in the middle of the army base that existed before Eureka was founded. They must find a way home before they change history or get caught.
Warren Hughes makes an unexpected visits to evaluate the Astraeus crew. Unfortunately his evaluations coincide with crew members' tendencies to swap minds with Jack. And some of the swaps happen during amorous activities that further stress the relationships of the crew's lovers.
Following its accidental launch the Astraeus returns to Eureka and the crew discovers four years have elapsed in an instant. The crew quickly learns leadership has changed, procedures have changed and relationships have changed while they were gone and none of it for the good.
The ship is finally found but the crew has been taken. When Carter is tasked with attempting to rescue the kidnapped crew by following them into the virtual Eureka, will he be able to get them out before their matrix world collapses for good?
As Grace (Tembi Locke) finds a way to share her memories with Henry (Joe Morton), the rest of Eureka's citizens face the return of people from the recent - or not so recent - past.