After being knocked out in a surprise blow from HG Wells, Pete and Myka shake themselves back to consciousness to find that Warehouse 2 is filling with sand. The only exit is blocked, and just as they think it's too late, Artie shows up and saves them from being buried alive. They head back to good ol' Warehouse 13 to deduce which artifact HG was after and, with a hand from Mrs. Frederick, realize that it was a spear. Claudia, meanwhile, has been tracking HG's spending, and Myka and Pete follow her to Paris, where her daughter, Christina, is buried.
At the grave site, Pete and Myka stop HG, but she outmaneuvers them and slips away. Myka notices something missing from Christina's casket, however: HG took a C-shaped handle from her daughter's coffin. Bringing this information back to the Warehouse, the team realizes that the handle, along with the spear, form a trident, an ancient artifact that has the power to create earthquakes, activate volcanoes, and even create another ice age. And when Claudia tracks HG on her way to Yellowstone National Park, home of one of the hottest geothermal spots on the planet, HG's plan becomes chillingly clear.
But things are about to take a new twist, as HG calls Pete to let him know that she's laid a special trap for his girlfriend, Kelly. Pete rushes to make sure she's safe, but gets a surprise when she attacks him with a knife. Claudia shows up just in time to realize that HG has sent Kelly Lizzie Borden's compact. She drops it in the neutralizing bag and Kelly snaps back to normal, but her relationship with Pete may be permanently damaged.
Myka and Artie find HG just as she's preparing to stab the trident into the earth - if she does so three times, the world will be trapped in another ice age. Artie breaks with custom and attempts to shoot her, but she's wearing an artifact that boomerangs any physical hurt from her onto the inflictor, effectively causing Artie to shoot himself in the shoulder. Thus disadvantaged, Myka's only recourse is to reason with HG, imploring her to look to the connection between them, and finally putting HG's gun on her own forehead and ordering her to shoot. This risk of her life finally gets through to HG: she breaks down and surrenders.
Once HG has been taken into custody and the team regroups, Pete attempts to talk to Kelly about the artifact episode, but he's too late: Kelly wants no kind of dangerous life, and so leaves the relationship. And Myka, after being horribly wrong about HG's character, loses faith in herself as a Warehouse agent. She writes a heartfelt letter to Artie, Pete, Claudia and Leena - and leaves the Warehouse.