Complex sentence: He has hidden them inside a computer simulation in a nuclear submarine base occupied by the Children of Atom as a sign of good faith, but has grown increasingly concerned that if the Children access the memories, they will have the means to destroy Far Harbor.
Split into simpler sentences: He has hidden them inside a computer simulation in a nuclear submarine base occupied by the Children of Atom as a sign of good faith. But he has grown increasingly concerned that if the Children access the memories, they will have the means to destroy Far Harbor.