The Hidden (Animorphs Series #39)

We can't tell you who we are. Or where we live. It's too risky, and we've got to be careful. Really careful. So we don't trust anyone. Because if they find us...well, we just won't let them find us. The thing you should know is that everyone is in really big trouble. Yeah. Even you.

The pint-sized Helmacrons may have departed Earth, but they haven't finished causing trouble for the Animorphs and Ax. They left behind a damaged ship-containing morph-tracking technology. Now the Yeerks have fou...