It's pretty clear that Nod won the elections so once the gang comes back to Nod's Limbs, the twins convince Nod to become the new Mayor so the twins won't go to jail for the incident with the stage and rats nor be forbidden to prank.
According to Madame Dahlia, with each visit always came tragedy and "mysterious misfortune" so Nod somehow has to sacrifice himself to save his friends and after Nod dies the twins decide to go back to living alone in Nod's Limbs but the Heimertzes convince them to join the circus and the Midway Irregulars since they are grateful to them for saving them and maybe Ellen becomes the Irregulars' second-in-command.
...hence the "around-the-world" trip.
She didn't start trying to take over the world or kill anyone until the Nodyssey books — after she'd been driven out of town and managed to take a bucket of balm with her, which she could have been using for months before she returned to Nod's Limbs.
Hence the sign on the Tower Mansion's front door, although it may be something similar and the twins altered it.
In "Split Ends", Edgar refers to the Midway Irregulars as "Imogen and the rest" and appeared somewhat reluctant to admit he didn't need her.
