On a Sunday morning, Lupo, Henry, Allison and Kevin worship at Eureka's sparsely attended church, where Reverend Harper, a former physicist, preaches. Suddenly, across town, Zoe loses her voice in an instant. She can't speak a word. Later that day, Allison's skin begins to glow. Stark diagnoses it as a form of bioluminescence and discovers that it is wreaking havoc with her nervous system. If it can't be stopped, Allison will die.

Meanwhile, the biologist Seth Osborne witnesses the water in one of his aquariums apparently turn to blood. Jack, already worried about Zoe and Allison, spots a vital clue at the scene: the aquarium's crystalline glass filter has a hole burned through it. Jack has found a similar hole in the crystalline glass skylight Zoe was sitting beneath when she lost her voice, and he soon finds a matching hole at Allison's house. All three incidents are related.

original airdate--September 11,2007

song--Eureka Theme song--"Eureka On My Mind" by Bear McCreary