Editing Foundation (book series) (section)

===''Second Foundation'' (1953)===
{{main|Second Foundation}}
As the Mule comes closer to finding it, the mysterious Second Foundation emerges briefly out of hiding to face the threat. While the first Foundation has developed the physical sciences, the Second Foundation has been developing Seldon's mathematics and the Seldon Plan, along with their use of mental abilities. The Second Foundation launches an operation to deceive and eventually mind control the Mule, whom they return to rule over his kingdom peacefully for the rest of his life, without further thought of conquering the Second Foundation.

As a result, the first Foundation learns something of the Second Foundation beyond the fact that it exists, and comes to have some understanding of its role. This means that their behavior will now be influenced by that knowledge, invalidating the mathematics of the Seldon Plan and placing the Plan itself at great risk. The First Foundation starts to resentfully consider the other a rival, and a small group secretly begins to develop equipment to detect and block the Second Foundation's mental influence. After many attempts to infer the Second Foundation's whereabouts from the few clues, the Foundation is led to believe the Second Foundation is located on Terminus (the "opposite end of the galaxy" for a galaxy with a circular shape). The Foundation uncovers and eliminates a group of 50 members of the Second Foundation, believing they have destroyed it.

The 50 were volunteers who sacrificed themselves so that humanity's collective behavior would once again be predictable and follow the mathematics of the Seldon Plan. The Second Foundation is revealed to be on Trantor, the former Imperial homeworld. The clue "at Star's End" was not a physical clue but based on an old saying, "All roads lead to Trantor, and that is where all stars end".