The Warehouse team struggles with the horrible reality of the Warehouse's destruction and the tragic loss of Steve Jinks, Mrs. Frederic, and H.G. Wells. With matters so desperate, Pete, Myka, Artie, and Claudia must decide whether to knowingly use a dangerous artifact for their own personal gain - at the risk of deadly consequences.
Pete and Myka are sent to Philadelphia to find an artifact that is the cause of strange hallucinations-people are fearing monsters, but when attacked, only humans are killed. Artie is searching for more information on what evil he unleashed. Claudia tempts fate as she tries to bring Steve back, with the help of someone unexpected.
A cache of Walter Skyes' stolen artifacts turn up and all six agents go into the field to recover them. Artie unexpectedly reveals his secret to Leena, while Steve begins to realize the downside of the metronome that brought him back to life.
Pete and Claudia reunite with Hugo to track down a deadly artifact at his nephew's prep school; Myka and Steve investigate an artifact that is killing a musician in New Orleans.
Pete and Myka investigate a hockey player who is miraculously recovering from his injuries; Claudia is invited to a mysterious lunch with Mrs. Frederic; Artie and Steve has discovered that someone is stealing artifacts from the warehouse.
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 grouping of Steve, Artie, and Claudia take a mission to follow Brother Adrian to discover where he has been hiding. Meanwhile, a brand new drug has emerged with the ability to increase people's height, so Myka and Pete must face a powerful company executive to try and put a stop to it.
Pete and Myka investigate a case of people rusting away; Steve and Claudia visit Steve's hometown to end his dependence on the Metronome; Artie tells the truth about Brother Adrian and his use of the Astrolabe.
Brother Adrian sends deadly artifacts to the agents loved ones; Mrs. Frederic and Steve discover the truth about Artie and Adrian.
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.
If Pete, Myka, Claudia, and Steve can't reverse what Artie has done, the world will be engulfed by the deadliest pandemic since the Dark Ages. But the Team is already succumbing to the disease's symptoms as they race to stop the artifact sickness - before it stops them.
While Pete and Claudia travel to Oregon to look for an artifact used to hug enemies of the environmental movement, Artie deals with the repercussions of Leena's death.
Pete and Myka get sucked into a 1940s detective noir novel in search of an artifact. Meanwhile, Artie, Steve, and Claudia chase down a phantom car thief.
While Pete and Myka travel to Las Vegas to investigate two deaths where the people inexplicably fell from great heights, Claudia and Steven investigate two jockeys in London who went into comas after winning their races. Meanwhile, Artie gets a visitor to the warehouse.
H.G. has created a new life for herself in Wisconsin, but calls in the agents when she comes up against an unidentified artifact. Meanwhile, Abigail joins the others on the floor of the warehouse to track down the source of mysterious tremors that threaten to destroy the building.
When a volcanic event at an Arkansas State Prison allows two inmates to escape, Pete, Myka and Steve must partner with a U.S. Marshal to track down the fugitives.
When residents of a posh gated community start getting affected by a mysterious, versatile artifact, Myka and Pete investigate.
The agents track down a cache of artifacts stolen from Warehouse 12 by the infamous Roaring Dan Seavey... and guarded by his ghost. Meanwhile, Charlotte Dupres makes her move with the help of her inside person.
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.
The team must capture Paracelsus before he achieves immortality, or worse. At the same time, Myka seems to be losing her battle against cancer; and Steve learns that Artie has been keeping life-changing information under wraps.