The new Star Wars book that celebrates the 40th anniversary of The Empire Strikes Back reveals when Palpatine finally figured out that Luke was Darth Vader’s son.
As we know, Obi-Wan Kenobi, Master Yoda, and the remaining Republic loyalists went to a lot of trouble to hide the circumstances in which Padme Amidala died. The sole reason was to keep the supposedly Force-sensitive twins, Luke and Leia, from the Emperor’s reach. As such, neither Palpatine nor Vader knew about the identity of the Rebel Alliance hero who blew up the Death Star until Episode V.
Of course, other canon sources have confirmed that the former Chosen One learned about Luke soon after the events of A New Hope, though according to the latest revelation in From a Certain Point of View: The Empire Strikes Back, which retells the events of the film from the perspective of other characters, the apprentice kept this information from his master.
In the chapter dedicated to Darth Sidious, we see the dark lord moments before he summons Vader to discuss Luke, witnessing several disturbances in the Force. One of them, in particular, shows him a vision: Vader’s fantasy of overthrowing Palpatine, but instead of being in his black suit and respirator, he appears as a much older Anakin with Padme and Luke by his side, the latter of whom strikes down the Emperor.
It’s here when Palpatine finally learns the truth. He also acknowledges that while Vader’s relentless hunt for the Rebel Alliance leadership may have been a little over the top, it now made more sense since the apprentice was looking for a way to overthrow Sidious.
The recent tie-in Star Wars book also reveals that as Palpatine talks to Vader about Luke, he senses his “struggle to control his desires,” confirming his suspicions that the seemingly loyal apprentice is indeed hatching schemes of his own.