When we last left agents Myka Bering and Pete Lattimer at the conclusion of season 2, Myka had decided to leave the top secret team with little to no warning. As season 3 begins, Artie fills Myka's shoes with 'The New Guy,' which also happens to be the name of the season premiere episode.

While Pete and Myka go after someone using an artifact to induce Alzheimer's, Claudia goes on her first case as a full agent with Steve to track down Typhoid Mary's knife.

While Artie and Claudia meet with Vanessa Calder and Hugo Miller to investigate a computer virus that transforms people into clay, Myka and Pete wake up naked in bed and try to find a missing Steve.

Pete's ex-wife arrives in town to remarry, but an artifact may derail the wedding. Steve and Claudia visit a Civil War reenactment in search of an artifact

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.

While in Denver, Myka picks up the trail of the counterfeiter who killed her former partner, Sam Martino. Meanwhile, Artie, Claudia, and Steve interrogate a dog that witnessed the theft of an artifact.

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.

While Pete and his mother Jane try to determine the origins of their mysterious opponents, Myka and Claudia travel to Portland to stop a girl who can apparently vaporize anyone she hates with blasts of radiation.

Myka and Pete deal with a plague of zombies in Ithaca, while Claudia deals with a new romance, a prophecy of death, and a rejection from a friend.

As Sykes begins his end game, the agents discover that Helena is still alive... and teaching high school literature. Meanwhile, Jane reveals the full extent of her plan but one agent will lose their life carrying it out.

Pete and Myka race to stop Sykes from using his own cache of artifacts to destroy them and the Warehouse.

Pete Lattimer is hit in the head by an artifact and wakes up to a life where he was never born. Pete must hunt down and persuade the Warehouse team (none of whom recognize him) to go on this life or death mission with him to vanquish a long dead nemesis from the past to get everyone’s lives back.

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.

While Claudia tries to help a friend and gets unexpected help, Pete and Myka investigate an artifact that causes crowds to see certain individuals as monsters... and attack them.

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.

While Pete and Claudia help Hugo Miller track down a bag of marbles at a boy's academy, Myka and Steve travel to New Orleans on the trail of another artifact while Artie meets with Brother Adrian.

While Pete and Myka go to Toronto to investigate an invulnerable hockey player, Steve helps Artie track down stolen artifacts while Claudia meets with Mrs. Fredericks to discuss her future as a warehouse guardian.

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.

While Pete and Myka investigate a series of artifact-related growth spurts, Artie reluctantly takes Steve and Claudia with him to track down Brother Adrian before he can steal more artifacts from the warehouse.

While Pete and Myka travel to West Virginia to investigate a rust-like infection among steelworkers, Steven and Claudia go to Steven's home to find a way to break the metronome's hold on him. Meanwhile, Helena, Leena, and Mrs. Frederic confront Artie with their knowledge of what he has done.

Pete, Myka, and Claudia set off to rescue their loved ones when Brother Adrian sends them deadly artifacts. Meanwhile, Mrs. Frederic and Steve travel to Rome and learn Adrian's dark secret.

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.

With the fate of the world in their hands, Pete and Myka's only hope of finding a cure to the Sweating Sickness is a drunken history professor. Meanwhile, Steven and Claudia enter Artie's subconscious in an attempt to bring him out of his coma before he fades away for good.

While Pete and Claudia travel to Oregon to look for an artifact used to kill enemies of the environmental movement, Artie deals with the repercussions of Leena's death.

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.

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.

Pete, Myka, and Steven team up with a U.S. Marshal to track down two prisoners who used a lava-spewing artifact to escape prison. However, they discover that the Marshal is Steve's ex. Meanwhile, Artie and Claudia try to track down part of an artifact that is rendering Artie deaf...

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.

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.

Pete and Myka capture Paracelsus but not before he makes himself immortal. When Myka's cancer becomes worse, Pete must make a deal with Paracelsus to cure his partner. Meanwhile, Claudia receives some startling news from Artie.

When Paracelsus takes control of Warehouse 13, it proves to only be the first step in his plan to recreate the entire world in his image. To stop him, Pete and Myka must follow him back through time to 1541 and prevent him from killing the Regents and becoming the permanent master of the Warehouses.

While Pete and Myka team up with two former Secret Service co-workers to investigate a series of bizarre deaths in Washington DC, Artie agrees to show Claudia how and why her sister had to disappear.

While Pete and Steven check out a life-threatening incident at a renaissance faire, Myka agrees to help Claudia revive her comatose sister. However, they discover that doing so has unexpected consequences that threaten the warehouse and everyone in it.

Pete's former girlfriend Kelly Hernandez asks him to help her find her missing grandmother, and the trail leads into a cancelled telenovela. Meanwhile, Artie forces Claudia to go with Steve to investigate the case of a college student of whose spine broke in the middle of a classroom presentation.

The alternate-timeline Valda makes his move, using Claire as his mindless slave. As Valda sets out to move Warehouse 13 to a new location that he can control, the team races desperately to stop him before it's too late.

While the team deals with the news that Warehouse 13 is moving, Mrs. Frederic has them load their greatest memories of their missions into an artifact for future generations.