At the smart house, everyone's a little skittish: Allison because Jo is still living with Carter, Carter and Jo because Allison's skittish, Jenna and Kevin because Carter is cooking, and SARAH because… well, who knows, but something called "RF interference" is causing her to burn the toast.

Carter and Allison have a lovely day planned for the kids, but this being Eureka, it gets interrupted when a giant fireball is loosed in GD. Parrish had been developing what he calls a firefly, a collection of nanoparticles designed to extinguish fires, but when he gets into a fight with Zane, the firefly goes crazy and does the opposite of whatever Parrish directs it to do. Carter tries to catch it, but it escapes his clutches and flies away. The only chance they have of catching it is to follow it to whatever heat sources it might attempt to extinguish.

original airdate--May 7,2012                        rating--1.45 million

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