Sight Unseen

S2, E9: An abandoned research project on invisibility returns to haunt Eureka. A break-in at the pharmacy in which the only thing missing is polyethylene glycol, starts a chain reaction of strange occurrences. First Zoe's car seemingly collides with an invisible object, and then disappears from its parking spot, only to be crashed into by another car trying to park. Carter consults Allison and Nathan about the polyethylene glycol, only to find that it is a harmless compound used as a base for everything from shampoo to pancake syrup. They, however, inform Carter of a not so harmless compound. Two tons of moon rocks, housed at Global Dynamics and dormant for 40 years, have suddenly begun to change their molecular structure and form radioactive crystals. It appears that the moon rocks are missing Aluminum 26, a highly unstable radioactive element. Carter and Jo go to check on a dog that appears to be barking at nothing, and find a bottle of polyethylene glycol, a plastic bag lined with crystalline residue and a syringe. Henry puts the two things together and realizes that Aluminum 26 and polyethylene glycol are key ingredients in an abandoned formula to create invisibility.