Warning: The following article contains spoilers for Arcane season 2 act 3.
While everyone’s favorite, mentally unstable inventor made a return from the otherworldly dimension in Arcane Season 2 Act 2 just to get a whole bunch of other innocent people killed, Professor Heimerdinger and Ekko were nowhere to be seen.
So what happened to these two characters and why didn’t they return to Piltover alongside Jayce?
The first episode in Act 3, “Pretend Like It’s the First Time,” opens with Ekko waking up in an alternate dimension next to Powder. In this reality, Powder has not turned into Jinx, and the two of them are working on a science project in the now-utopian Zaun. Vander and Silco are tending to their bar, Benzo is still around, and all around it seems like this new reality has hit the jackpot out of all the alternate dimensions. The only catch is that Vi had to die during that first job in episode 1, which kickstarted this entire story, for everything to pan out this way.
Ekko is confused by all the anachronism of this new reality, but not for long. He stumbles into Heimerdinger, who tells him he has lived in this reality for over three years. He also plays the guitar now, so take from that what you will. Heimerdinger tells Ekko that he can find things to appreciate in this world too, but the Boy Savior eventually convinces both Powder and Heimerdinger to create another hex machine so the two can go back to their own timeline.
What happened to Heimerdinger? Where did Ekko go?
Ekko ends up creating his time-travel weapon from the League of Legends game, which allows his champion to travel 4 seconds back in time. Heimerdinger amplifies the machine to zap them back to their reality, but not before Arcane gives all those “Timebomb” shippers what they’ve been asking for 3 years. Ekko, or this doubleganger version of himself, steps into the machine with Heimerdinger but things go awry. Heimerdinger sacrifices himself to let Ekko through, which finally turns him into the Ekko we know from the main series. The alternate Ekko gets separated and rejoins Powder, while our Ekko goes back to Piltover.
As for Heimerdinger, it’s unclear what happens to him, but he also disappears the moment the machine is fully activated. Given the fact that we don’t see the professor in the remainder of the episodes, it’s safe to say that Riot Games has plans for him in the other League of Legends-inspired series currently in development. It could also be that Heimerdinger remained in the alternate dimension, where he seemed to have made quite a fresh start for himself, but then, why would the show make him disappear if that was the case?
Whether this was an oversight on the writers’ part or an intentional plug to keep us guessing is unclear, but for the time being, your guess about the fate of Heimerdinger is as good as ours.