Winnie and Tuck go out on the pond in a small rowboat. It's a picturesque, beautiful time of day, and the sun is setting. Great postcard material.
Different types of wildlife surround them, and Tuck tells Winnie that they are seeing "Life" itself in all this nature and movement. Adding to the serious stuff, Tuck tells Winnie that life "[is] a wheel" (12.6) that continues to move around.
At that point, their boat slides into a tree and stops moving. Tuck hits us up with a metaphor, telling Winnie that he and his family have become like the boat: they aren't going with the natural order of things. (Having trouble with all the metaphors and comparisons? Check out the "Symbols, Imagery, Allegory" section and get a little TLC.)
For the first time, Winnie realizes that she, too, has to die someday. Oh boy. This moment isn't fun for anyone. It's a complex and difficult thing to consider—so she promptly rejects it.
Tuck makes her think about it, though. He says that it has to happen to everybody sometime, and it's wrong that it won't happen to his family. He'd like to go back to the way things were. He doesn't want to be immortal.
Tune in for this key moment: Tuck makes a passionate argument against immortality. We suggest you go back and check it out for yourself.
Winnie is overcome by a bunch of different thoughts. Before she gets a chance to say anything, though, Miles calls out to them that the family's horse has been taken away.