It's quite a welcome when Pete and Myka arrive in St. Louis: Six body bags fill the police station. Captain Powell seems to think it was simply a gas main that ruptured and ignited but, in the basement, our team finds the remains of a long-dead Warehouse agent! At the Warehouse, Claudia and Artie make a match - the agent is Jack Secord, recruited to the Warehouse in 1955. Artie's clever pencil rubbing on a left-behind pad of paper among Secord's persona effects reveals "Rebecca" and an address in St. Louis. Soon after Artie finds the clue, Pete and Myka are in Rebecca's living room breaking the news to her about her presumed boyfriend, Jack. Before the full extent of her relationship to Jack is revealed, the duo is called away.
In an empty lot, they find a new collection of body bags. Powell scoffs when a kid in the crowd tells them the killer was a cop, but Pete and Myka decide maybe they could use the expertise of Sergeant Clark, leader of the Gang Unit. The two enter Clark's apartment, where he's crouched in the open window, the air around him crackling with electricity. Attached to his back is what looks like a rusty metallic lobster with an eerie glow. Before they can stop him, he jumps. Pete and Myka find Clark's lifeless body behind a dumpster - the metallic lobster gone.
Myka realizes Rebecca knows more than she's letting on, and her suspicion is confirmed when the duo realizes Rebecca wasn't just Jack's girlfriend; she was a Warehouse agent! She explains that the burned bodies started appearing shortly after an 11th Century exhibit arrived in the city. Artie confirms the missing exhibit is "The Spine of The Saracen," a weapon designed for the warriors of The Crusades.
Back at Clark's apartment, gunshots ring out. Pete and Myka witness a woman chased by a man who has been overtaken by the Spine. The Spine drains the last bit of human energy from the man before detaching and latching onto Pete! He cries out in pain as the Spine fuses itself to his back but, determined not to be a mindless killing machine, he escapes to kill himself, just as Jack Secord did. Myka breaks the news to Artie and Claudia, but the Warehouse's whiz kid suggests the Spine's receptors might detach if overwhelmed by an electrical charge. Powell and Myka remember the police station's generators - Pete has found his charge!
Myka, Powell and Rebecca arrive at the station to find Pete raging, convinced he has to die. When Myka can't bring herself to electrocute him, Rebecca strides to the generator and grabs the cables, quickly clamping them to the Spine. In a brilliant flash of light, the Spine drops to the floor, lifeless...followed by Pete. Refusing to give up, Myka begins CPR on Pete until he finally gasps for breath. Later, Artie is tolerating Pete's amusingly weary attitude when Rebecca enters with Myka and the remains of the Spine of Saracen. Before she goes, Rebecca has a dire warning for Myka: "Get out while you can. This place will use you up."
On a rainy day at the Warehouse, Pete accidentally triggers an artifact that transforms the team into two-dimensional diorama versions of themselves, and returns the Warehouse to its original, unstable design.
Who knew Claudia had those moves?! OK, so maybe they're artifact-induced, but we're so in love with the spangles, we don't care!