Fearing that Claudia is central to the evil unleashed when he used Magellan's astrolabe, Artie makes Claudia's location his sole priority, sending Pete and Myka off to Philadelphia to investigate the beating of a man by an angry mob who all agree he looked like a large, tentacled monster. Pete and Myka can't find any connecting factor between the various assailants, and when a similar death occurs at a dentist's office across town, they're even more stumped. They're at their wits' end when they get a call from Lena telling them that a man just lodged a police call saying that a monster had invaded his house. The local police dismiss the call as fluff, but Pete and Myka rush over.
They find a man with a shotgun pointed at a closet door, where he's trapped the "monster." They disarm him and find the man's wife, cowering in a ball. They learn that she had a normal day, except for the man in black with a baseball cap who tried to give her a small, silver key. They run the description past Lena, who tells them that it's the key of H.P. Lovecraft, an author who created many a tentacled, fictional beast. Searching the first victim's apartment for clues, they find a souvenir from a basketball game - the same game as the baseball cap worn by the man with the key.
Reviewing the security footage from that game, they see a man, Ron Hadsell, trying to save his fiancée from getting trampled to death by the rioting crowd. He turned to many people for help, and they denied him. Myka and Pete recognize these people as the victims, and there's one more person who wouldn't help - could he be Hadsell's next victim?
Myka goes Hadsell's house while Pete seeks the potential final victim - but Hadsell is already there. Pete gives chase and Myka catches up, and when Ron hits Pete with the key, Myka defends him from the fearful crowd. She sees Hadsell and tackles him, throwing the key into a purple bag just in time to break the spell and save Pete's life.
Artie isn't faring so well: though he located Claudia, Jane steps in while he tries to talk her out of resurrecting Jinks and tells them both that the Regents have given approval to bring Jinks back. Jane guides Claudia through the resurrection process, and though he's shaken, Jinks is alive. That's all that matters to Claudia, until Mr. Kosan arrives and tells her that Jane acted without authority, and no one has any idea what the side effects of using the metronome could be. Now, everything Claudia is and has lie on the line.
Artie thinks back to earlier that week, when he was visited by Father Adrian, head of the Knights Templar, who warned him of the great evil that Magellan's astrolabe would unleash. Though he promised Adrian to find the astrolabe and reverse its use, secretly he's trying to find another way to make things right. But as he receives a ping, he knows the evil is on its way: a dagger has been located, and it's the same one he saw Claudia, in a vision, use to attack him.
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.
Get a laugh with the best lines of Warehouse 13 Season 4, Episode 17.