How could Karen go free?

Question

Due to her interaction with Cassie, Aftran decided to let her host, Karen, go free. Near the end of #19 The Departure, Aftran is inside Karen's head, in the woods, talking to Jake. Karen's body is very badly injured.

At the very end of the book, Cassie meets Karen, finding that she is indeed free.

In #29, Aftran is found to also actually be unhosted in the pool, as promised. She also risks her life to save Ax's, then voluntarily leaves Ax's head.

Aftran freed Karen and then went back to the Yeerk pool to live there without a host.

How did Aftran get down to the pool, if not through Karen's body? How could a lone Yeerk travel down to the pool without a host? And if she used Karen's body to get down there, the Yeerks would not let Karen go, they'd either give her to another Yeerk or kill her (due to her injuries).

One thing I can think of is that Aftran could have done something like what Illim, Tidwell and Cassie did in #29. For example, Aftran could have traveled to Tidwell's house in Karen's body. She could have then left Karen's body. Tidwell and Illim could have then taken Aftran to the Yeerk pool in a container, like he did to Cassie's Yeerk-morph in #29.

However, Aftran is thought to have been one of the first members of the Yeerk Peace Movement. And she only joined/formed the Movement after and due to her interactions with Cassie. This would indicate that the Movement might not have existed at the time. If it did, could Aftran have had connections with it? At the time of meeting Cassie in the woods, Aftran seemed like a normal, aggressive, unsympathetic Yeerk.

Assuming that she didn't have any connections to anyone in the Yeerk Peace Movement at the time, how could she make it down to the Yeerk pool without Karen?

I've also considered the possibility that when Cassie met Karen at the end of #29, Aftran was actually still in Karen, pretending to be the free Karen. But then, how did Aftran end up unhosted in the pool (as she did) without giving up Karen to another Yeerk? If another Yeerk took over Karen's body, then the Yeerks would have learned about the Animorphs from Karen's memories. That didn't happen.

How did Aftran make it down to the pool without Karen?

Assuming she somehow did, could Karen remain free? If Karen was once a controller, would the Yeerks wonder what happened to her? She was a small child, and the Yeerks were tracking her dad. When Aftran was being held in the pool, unhosted, suspected of treason, would the Yeerks perhaps have wondered what happened to Aftran's previous host? If they did recapture Karen, her mind would contain information about the Animorphs.

Why did the Yeerks ignore Karen after she was freed?

Answer 1

Not really, the thing is Karen was not high ranking enough. It would take at least three days for the Yeerks to notice her not getting back into the pool. Even then it is highly likely the Yeerks would just think they missed her, I doubt they take stock of every random controller coming into the pool. By the time they realise that Karen is not infested anymore Aftran has probably hidden deep within the pool with the Yeerk Peace Movement so it's hard to find her (though they eventually do). As for Karen, well first of all she is a child so not a huge security breach (no one would believe a child talking about an alien invasion) and the fact that she would have been out for a while without raising the alarm means that she won't be drawing unwanted attention. Therefore, the Yeerks know that Aftran isn't going anywhere and they will eventually find her, know that Karen can be reinfested any time and that doing so is not a priority, so they basically let her go free for now (not realising that their invasion's days are numbered) and focus on finding Aftran (which they do and then she is sprung by the Animorphs). After that they figure that they realise what happened, Aftran became an Andalite sympathiser, and Karen doesn't know anything because we all know that Andalites don't share information, so there is nothing she can say and that she is very likely being watched by the Andalites so attempting to reinfest her would lead to a violent death for the Yeerk who tried it