Turtles

Here's a symbol that comes at you like an anvil (see "Symbols: The Puzzle" for another): baby turtles. Let's let Nadia explain it:

When baby turtles come out of their shells, which are round—about the same size as a golf ball—they are squinched up into a round shape that fits inside the eggs. After they break through the shell, they spend three days down in the sand hole straightening themselves out. Sometimes they die before they make it out of the shell. Those are the dead-pipped. They are counted and discarded with the unhatched and the empties. A permitted person has to decide if the live-pipped are more alive than dead. If the decision is that they stand a good chance of surviving, they need care. They are lifted from the nest and taken home and given shelter until they straighten themselves out, and then they are released onto the sand. ("Nadia".78)

If it weren't for people coming in and physically moving the turtles around, many of them wouldn't survive. Know who else gets physically moved around? Nadia, Ethan, Noah, Julian, and Mrs. Olinski.

• Nadia: "I, too, had been picked up from one place and set down in another. I, too, had been stranded. We both needed help resettling" ("Nadia".231). 
• Mrs. Olinski: "She was on the verge of screaming with pain and rage when she felt her wheelchair begin to move. She felt herself being pushed toward the front porch of Sillington House" (5.30)
• Noah: "Fact: I had not been their houseguest by choice because fact: She [his mother] had sent me to them" ("Noah".2)
• Julian: "I am a passenger / on Spaceship Earth" ("Ethan".69)
• Ethan: "Something in Sillington House gave me permission to do things I had never done before. Never even thought of doing. Something there triggered the unfolding of those parts that had been incubating. Things that had lain inside me, curled up like the turtle hatchlings newly emerged from their eggs, taking time in the dark of their nest to unfurl themselves" ("Ethan".258)

Okay, the last one is a bit of stretch, but you get the point. They're travelers, but not of their own volition. They get picked up and moved around—and then realize that they're where they always wanted to be in the first place.