Quite pathetic script and episode. The sheriff handles himself like a Victorian-era prude, cartoonish rocket "special" effects, Dr Blake's lack of ethics, ... ugh!!!
It is another scientists gone awry and endangering the world to save it again. This time rockets have been sent on a race around the moon, but their return to Earth poses a threat that the scientists of Eureka must deal with. The characters -- formerly likeable -- have been made unlikeable. Dr Blake is selfish; Sheriff Carter is a prude; Zane is a bad boy (although he seems to come around a bit at the end of the episode and be seen in a different light).
However, the addition of Dr Grant (James Callis) has been a plus. Hopefully, the following episodes will show an immense improvement; otherwise it bodes ill for a season 5.