Check out the official description, of the 3.21 episode of "The Flash".
Team Flash is yet to unveil the identity of Savitar! Check out what happens in the third season of 'The Flash', ‘I Know Who You Are’.
In 'The Flash: Season 3, Flash is seen defeating Savitar and snatching the Philosopher's Stone which gave him immense powers. Now he has to dispose it so that it doesn't lands in evil hands. Henry Allen helps Barry to throw the Philosopher's stone above where Barry sees his girlfriend getting killed by Savitar