|From Fear to Eternity|
|Air date||September 23, 2008|
|Written by||Thania St. John|
|Directed by||Eric Laneuville|
| Preceded by|
"Here Come the Suns"
| Followed by|
"Welcome Back, Carter"
|Cast | Transcript|
|Season 2||Season 4|
A doomsday weapon built in the abandoned military complex is discovered, as is the secret Thorne wants to stay hidden – she's 107 years old, real name Mary Perkins, and was involved in a pre-Eureka research project that developed the first atomic bombs (using radioactive material from meteorites). Meanwhile, Jo and Zane get stuck together, literally, and Zoe's life is imperiled by the aging syndrome that killed Mary's colleagues which she got from slipping in that puddle. Allison is found to be pregnant with Nathan's child. Thorne sacrifices her only chance for a cure for her condition to save Zoe, but the radiation that caused the aging condition is released into the town. The team realizes that the scientists managed to create a cure: the doomsday bomb in the bunker was a fail-safe to neutralize the radiation if it ever got out and the scientists ran out of time to use it on themselves. The bomb is triggered and the town is saved. Meanwhile, Jo and Zane are finally freed and renew their seemingly failing relationship. After Jack lets Thorne go to find a new life as he feels she's a victim too, General Mansfield tells Carter that his services are no longer needed by the town of Eureka.
- Colin Ferguson as Jack Carter
- Salli Richardson-Whitfield as Allison Blake
- Joe Morton as Henry Deacon
- Jordan Hinson as Zoe Carter
- Erica Cerra as Jo Lupo
- Neil Grayston as Douglas Fargo
- Niall Matter as Zane Donovan
- Frances Fisher as Eva Thorne
- Barclay Hope as General Mansfield
- Vanya Asher as Lucas
- Ever Carradine as Lexi Carter
- Chris Gauthier as Vincent
- David Richmond-Peck as Dr. Hendricks
- Julius Chapple as Section 5 Guard
- Bridget Hoffman as Computer Voice
- Although the door is left open, Eva Thorne is never seen again in "Eureka".