After a strange accident sidelines Eureka's sheriff, U.S. Marshal Jack Carter takes over the investigation into the mysterious phenomenon that led to the death of a resident. Carter learns about the secret purpose of the town while trying to re-establish a connection with his angry and bitter daughter, Zoe. He develops a friendly working relationship with government liaison Allison Blake and meets some of the more eccentric residents of Eureka.

A recently deceased woman shows up at Carter's office; a ghost-like figure appears in Allison's home.

When a world-famous scientist visits Eureka, Carter and Henry realize that they cannot account for blocks of time.

Carter investigates Spencer's alleged abduction; Eureka's funding may be in jeopardy.

A researcher taps into the power of a dangerous artifact, intensifying Stark's obsession.

Stark, Henry, Fargo, Carter and Allison enlist the help of an aging scientist to stop a catastrophe.