This is a story about a girl who started off as invisible and eventually found her ‘anger’ and became visible.
Too-ticky brought an invisible guest in the Moomin family home. The Moomin family welcomed her especially Moominmamma who made her a dress and gave her medication/potion to make her visible again. Moominmamma looked after her and Ninny (the-invisible-guest-soon-to-be-visible-girl) followed her everywhere. One day, the family went on a picnic near the water/wharf and Ninny thought that Mommin pappa was going to push Moominmamma to the water (he was only joking; he wasn’t really going to push her in), so she bit his tail and then voila she became visible!
This is the second book in the Moomin collection that I have read. It’s quite a good story, aimed at primary school kids, about finding your voice.