Secret Service agents Peter Lattimer (Eddie McClintock) and Myka Bering (Joanne Kelly) are reassigned by the mysterious Mrs. Frederic (C. C. H. Pounder) to a top-secret facility in South Dakota. Now reluctantly joining the quirky Artie Nielsen (Saul Rubinek) as "gatherers and protectors" of empowered and potentially dangerous objects, Lattimer and Bering investigate a report of domestic abuse in Iowa and discover a small-town lawyer (Sherry Miller) who is channeling Lucrezia Borgia.

A string of bank robberies in Chicago puts Pete and Myka on the search for a very soothing song, while Artie probes a security breach in Warehouse 13.

After recovering a guillotine in Paris, Pete and Myka seek an inhibition-releasing artifact in the fictional town of Unionville, Colorado. The village used for filming was the actual village of Unionville, Ontario, Canada. Meanwhile, Artie, refusing Leena's (Genelle Williams) help, probes the strange energy surges plaguing Warehouse 13.

Artie gets kidnapped by the source of the warehouse's security breach, Claudia Donovan (Allison Scagliotti). She enlists Artie to help right a wrong from their past; namely, the disappearance of her older brother Joshua, which was caused by an artifact. Meanwhile, Pete and Myka try to uncover his whereabouts, against the wishes of Mrs. Frederic.

A thief steals a sculpture with the help of a Native American artifact, and the investigation leads Pete and Myka to discover a sacred place that they deem worthy of protection. Claudia sneaks into the team to protect herself from the organization's "consequences" for her actions.

While investigating the site of a presumed gas explosion, Pete and Myka are shocked to discover the body of another Warehouse agent. While considering their eventual fates as agents, they make contact with another ex-agent (Rebecca St. Claire, played by Roberta Maxwell) and find the artifact. Unfortunately, it promptly attaches itself to Pete, making him more aggressive and dangerously electric.

Pete and Myka return to Washington to intercept a samurai sword that is to be presented to the president, only for it to vanish before they can reach it. While investigating, they butt heads with their previous superior, who reveals an unfortunate chapter of Artie's past. Meanwhile, Artie looks into the whereabouts of James MacPherson, an ex-Warehouse operative whom he believes is involved.

Pete and Myka go to Las Vegas to fetch an artifact that is helping a married couple (played by Eureka's Erica Cerra and Niall Matter) to win at the Casinos, but the mission goes awry when Myka becomes trapped in Lewis Carroll's mirror.

Artie sends Pete and Myka to a prison in Florida to investigate reports of an unusually high number of unexplained suicides; while performing inventory duty at the warehouse, Claudia discovers a practical use for one of the artifacts without considering the danger involved. Guest-starring Eureka's Joe Morton.

After an accident, Pete, Myka, and Claudia are trapped in the warehouse with several artifacts activated and the neutralizer processor jammed. Unfortunately, the only way to fix things in time involves passing through the particularly dangerous "Dark Vault". Meanwhile, Artie is forced to answer for his and MacPherson's actions to his superiors, the Regents, including Benedict Valda (Mark Sheppard).

As the agents search for MacPherson, Myka's father (Michael Hogan) is sent and subsumed by Edgar Allan Poe's notebook. As it is a bifurcated artifact (one with multiple parts), Pete must track down the other half, currently in the hands of an embittered teenage scholar.

Artie, Pete, and Myka discover MacPherson's plan to secretly auction off artifacts, and rush to track down and stop him. Meanwhile, Claudia learns she's had connections with MacPherson in the past, and is accused of being a sleeper agent.