User blog comment:Kittyfire/Random Topic Blogging!/@comment-5495184-20111018141532/@comment-5495184-20111018151456

Alright:

After messing up a project and nearly killing people in the accident, Phineas disappears, leaving behind no clue of his whereabouts. After months pass, Phineas is presumed dead, but there are some people who refuse to let him go. As Ferb, Candace, and Isabella try and cope with Phineas' disappearance, they soon find out some things are better left unsaid.

(yay for vague-ness! :D Sounds dull and cliche right now, but trust me, the story itself is MUCH more interesting than this summary. )