welcome (back) in Gravity Falls

Three years after the Weirdamagedon passed, our mystery twins are back in Gravity Falls and nothing has changed much.
Expected for a new member in the Mystery Shack.

Who is that boy? Why does he seem familiar?
And what is going on between him and Ford?

Be ready to watch a former demon trying to make up for his crimes.

(Complicated BillFord and human Bill)