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.

When a series of mysterious disintegration deaths occur in Pittsburgh, the team discovers that the artifact responsible, Joshua's Horn, has ties to Helena's time as an agent in 1893.

Pete, Claudia, and Myka are called in to help Fargo, who is trapped in a virtual reality swords & sorcery game. Meanwhile, Artie and Steve are summoned to New York to recover an artifact... by FBI agent Sally Stukowski.

Sally Stukowski and her partner make their move, attacking the Regents and using an artifact to trap them in a building and bring it down around them.

In the aftermath of the warehouse's destruction, the Warehouse team races against the clock to find a way to undo time itself and put right what went wrong. However, Artie finds himself facing a difficult decision when he is warned that saving the warehouse will unleash an even greater evil.

The Brotherhood continues its assault on Artie's life, targeting someone close to him with Alice Liddell, the imprisoned spirit within the Dodgson Mirror. Meanwhile, Claudia learns of the connection between her and Steven.

The team have no time to mourn a fallen comrade as they go after the person responsible, the nemesis that has been stalking Artie since he used Magellan's Astrolabe to save the world.

A mishap with an artifact traps Pete and Myka in a fictional 1940s world where they have to solve a murder to escape... but someone doesn't want them to. Meanwhile, Claudia and Steven convince Artie to go along with them to investigate reports of stolen cars, and Artie starts taking dangerous risks.

Someone in a gated community is using an artifact to extract vengeance and Myka and Pete go to investigate. Meanwhile, Artie and Claudia help a teen suffering from dangerous visions, and Steven and Abigail clean up the warehouse.

Pete, Myka, and Charlotte must track down Sutton, the only man who knows where they can find Paracelsus and exchange the Philosopher's Stone for the stele that will free Claudia from her bronze imprisonment... before she disintegrates.