huck finn line.

So my teacher assigned my class, (advanced english) to finish the book Huckleberry Finn over the weekend. keep in mind this is over 20 chapters. ugh. but to make it worse i have to find a single line in the story that summarizes the entire book. and she knows what one it is... has anyone else had to do this? and if so.. do you know what line it might be. or even if you've just read the book.]]
i think it's in the last half of the book. or that's what she said.
thanks so much for your help. it'll mean a lot.

xo-Brittany