This is another Multiverse Investigations e-book that I downloaded, and is very short. It stands apart from the other stories, and I suspected it was written as a prequel.
In this story, Schrödinger is the main character, as Alex goes out to a Halloween party. In the meantime, Schrödinger meets the Quantum Witch, who invites him to sit on her broomstick. She didn't exactly seem to be a typical witch, as in this book she used her quantum powers to resurrect Schrödinger at one point (this was possibly meant to show how he became a "quantum cat" in the first place, and it turned out her motivation was to try and bomb the building where Alex was attending her party.
I thought this was enjoyable enough, with the characteristic humour that I'd seen in Murder in the Multiverse, and it had Schrödinger attempting to communicate with birds and humans, only to find that only the witch was able to speak cat.
This was an easy enough book to read, and I managed to read it in about 15 minutes.
Next book: The Shepherd's Hut (Tim Winton)