“If You Build It…” is episode thirteen of season three of Eureka.
Allison has given one of the Global Dynamics scientists carte blanche to build things for planetary defence against whatever is creating the incoming signal – which doesn’t go down that well with everyone else, especially when he detonates a rocket above the town.
A strange structure is being built out of odds and ends – including, quite literally, the kitchen sink – in a field outside of town. When Carter and Jess stake the place out, they discover that it is being assembled by the town’s teenagers, including Zoe, who don’t appear to realise what they are doing. Fargo, meanwhile, is having car problems.
As the source of the signal gets closer, Allison gets more and more worried, and it looks like the strange structure is connected.
The story doesn’t conclude in this episode, but continues in the next, “Ship Happens”.