Oh, Number Five. He's always stuck with the most burden of the work! When he lands in 1963 and sets forth to drag his siblings back to their original time of 2019, he does so with few details. When he convinces their father to meet up with them, hoping the man will have an idea for how they can return to 2019, Sir Reginald isn't able to give him any answers. But he does give him a word of advice to help with his time-jumping problems, "Start small." Sir Reginald reminds Five that "so much can change in a matter of seconds," which doesn't mean much to the former Commission agent at the time.
With his father unable to help, Five agrees to a deal with the devil Handler, travelling forward to 1982 to murder Commission's entire board of directors, leaving her in charge. In exchange, she gives him a time-travelling briefcase and a deadline to meet if he wants to return to 2019. Sadly, only Luther and Klaus make it to the meeting spot in time as Diego gets kidnapped by Lila, Allison gets waylaid by the remain two Swedes who attack her and Raymond at their home, and Vanya gets taken by the FBI who believe she's a Russian spy.
With another plan screwed, Five decides to intercept the version of himself that was sent to ensure the assassination of the President to steal his time briefcase. Luther tags along to keep him from going insane due to "paradox psychosis," but the older Five attempts to kill his younger self instead. Luther and young Five manage to roughhouse the older Five into the portal that will take him back to the point in time when Five originally returned to his family in season one, but the briefcase is destroyed in the struggle.
With all their plans failed, Five tags along with his siblings to help Harlan on Sissy's farm. They're attacked by the Commission agents under the command of the Handler and Lila, who vows to end the Umbrella Academy for good. When the Handler realises Diego is taking down Lila, she kills the Hargreeves and her adoptive daughter. Five manages to use the last bit of his strength to time travel the few seconds before the Handler came into the barn to kill them, saving them all. The final Swede assassin shoots the Handler, taking revenge for his fallen brothers. Five convinces him to leave them all alone, and after Vanya has helped Harlan reign in his power outburst, gets a briefcase to bring them all to 2019.