I really like the last line. It lets the reader finish the story however they want. Considering that it's the dead/undead world coming for a visit, I'm not going to make it very pleasant. Poor Sarah and Grant. Very cool.
That was a bit heartbreaking for me. If my wife ever cheated on me I don't think that I'd be mad. I'd be crushed. There was a lot of sweet moments between Jill and Dave which I think many people will be able to relate to. I can't really comment on punctuation or anything because mine is atrocious. Nicely done!