Cal and Zoe attend the execution of a man they helped put on death row. Moments before dying, the murderer claims to be innocent… and Cal believes him. Racked with guilt that he might have sent an innocent man to his death, Cal defies orders from the FBI to stay out of it and goes in search of answers.
Carter’s camping trip with Kevin becomes a little scarier than ghost stories by the camp fire when a malfunction with the AI at Global Dynamics may turn some of them deadly. Elsewhere, Henry thinks about telling Grace the truth.
When headquarters shuts down the house, the crew formulates a makeshift response to a nearby call. A face from the past stirs Tommy and Janet's emotions as their date begins to unravel.
In order to save the life of an insurance investigator named Sara Ellis, Neal and Peter have to find out why a real-estate mogul put a price on her head.
Mrs. Frederick secretly recruits Pete to find a mole within the organization who is buying artifacts. However, when the mole finds out, they go after those closest to Pete.
A strange clue in an empty room, a blood-soaked car, a priceless Old Master, a deranged bomber. With the clock ticking, the curtain rises on a battle of wits between Sherlock, John and the shadowy stranger who seems to know all the answers…
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.
Tommy loses his nerve when a young driver's recklessness reminds him of his daughter's new lifestyle. After a meeting fails to put Colleen on the wagon, Tommy is forced to pursue a more aggressive method to get her life back on track.
Mozzie fears that the object of his affection has been kidnapped, and turns to Neal and Peter for help.
Douglas Fargo of Eureka’s Global Dynamics is sent to Warehouse 13 to help update its aging computer system. This triggers a seemingly sentient computer virus that sends the Warehouse into lockdown and traps the team inside.