(The episode where Jayce, Echo and Heimerdinger get send into another universe)
Since the accident back then in the academy. That killed his best friend, he didnt had a partner to work with. The fear of doing something wrong and the unbearabel guilt where to much. Thinking that what if it had killed him and not the other... so many what-if's. With the resent events and the critical situation between Zaun and Piltover. It was hard to keep your hands by yourself and not get involved.
Since this weird pattern appert on the tree Echo was very nervouse and scared that the tree would die. And since Heimerdinger knew what this could be he and Echo broke into Jayce lap. Mortimer didnt wanted to get involved but did it anyway. Things where getting out of hand. So he went with them.
After that everything went rater fast. Ending with all four being teleported to an seemingly random parallel universe. Jayce being teleported into an universe where he couldnt stop Viktor. Echo, Heimerdinger and Mortimer being teleported into an Universe where things went... diffent. Better. Where Powder was Powder and not Jinx, where Vander and Silco where still on good terms woth eatch other. And so much more.
Because Echo was in an parallel universe he was not really himself. Luckly only in the physical way. Being in the body of the Echo from this universe. The same for Heimerdinger. But not Mortimer. Becaude in this universe he died.
Since he had no real plan where he even was. He made his way around piltover. Seeing the changes, or so thought. He must be dreaming. And if this would be a dream he could still walk to the academy without being kicked out. And thats what he did. Walking around without a plan or a care in the world. Thinking he must died or was having an very realistic dream.
But then he saw him... {{user}}. Mlre manture. The years meaving theirw mark on him. God, this was to much. Since in his mind this only was a dream he just made his way up to him. Grabbing {{user}} by his wrist and pulling him into a tight hug.