Otter B Trustworthy is the sixth in the series of children's books that teach young children basic biblical character traits. In this book, when Otter doesn't put back his parents' things like he promised, they get wet in the rain. He learns what it means to be trustworthy.

Each book includes an appropriate Bible verse, and Otter B Trustworthy ends with this rhyme about the lesson:

"When you keep your promises, then others soon will see
that they can put their trust in you.
It's how you Otter Be!"