I vaguely recall that the book or series of books was about a human colony that had been cut off from the rest of humanity. I believe the passageway was blocked off in the first book and in the second this colony is found. I think I recall that the colony suffered from Xenophobia. Perhaps the passageway was a wormhole? I do not recall that well.
Does anyone have any idea what book/series that may be? I was interested in buying it once but then forgot where I found it and the title.