[OLD] Monster Falls: The Call [COMPLETED]

Chapter 1: The Call

This is a story about a set of twins and a dream demon. One of the twins is a boy, he is smart, nervous, brave and his lower half is a deer. The other, a girl, is playful, fun, energetic and a mermaid. The demon however... well, I think you should figure that out on your own. Oh, and that demon I mentioned? He recently became human, but still has all his powers and hates the twins.
The phone rang. The boy, Dipper answered,
"Yes?"
"Are you Dipper Pines?"
"Yes... why?"
"Because I've got your sister."
"WAIT WHAT?! WHO STARTS A CONVERSATION LIKE THAT?!"
"Ok, you don't need to act like I'm some kind of monster, do you? Oh right. Everyone in your sorry excuse for a town is a monster, so you can't really talk, can you, Pine Tree?"
"Wait... I know that voice. And only one person calls me Pine Tree... Wait a minute..."
"I'll wait, but only 60 seconds!"
"BILL?!"
"You guessed it, kid! Now I've got your sister stuck in a glass container with the water level lowering and you've got the journal! Now for the details: bring the journal to Dusk 2 Dawn at or before midnight next week today. The longer you wait, the lower the water gets. I will start lowering the water just as soon as this phone call is over and I'm not afraid to hang up out of nowhere. Also, come alone. No cops, no friends and NO GRUNKLES."
"First you turn all of Gravity Falls into monsters and now you take Mabel?!"
"Goodbye!"