Saikawa and Moe are invited to legendary mathematician Tennouji Shouzou's Christmas party in his mansion Mitsuboshikan. While the guests are in the mansion's planetarium, the huge Orion statue in front of the mansion vanishes and the professor challenges his guests to solve this mystery. When the statue appears again later, the corpse of a guest who was supposed to have been in her room is found in front of it, while another corpse turns up in her room...
Nice. The setting and the extent of the mansion's resemblance to an attraction could just as well have been written by Ayatsuji Yukito. And the trick's eventually simple yet beautifully logical solution also reminds of Ayatsuji's suishakan no satsujin, in the way that the whole picture immediately becomes apparent as soon as you realize a certain fact. Mori actually states in his Mystery Workshop that he likes this work of Ayatsuji the most for said reasons so the inspiration became pretty clear for me knowing both works, even with the trick's basic category being fairly different.
Due to the trick's aforementioned nature the readers seem to be split into two groups as to this novel. All of them seem to be smarter than me and realized that single possibility due to certain clues and after that everything fell into place. What differs is that there are those who approve this simple yet logical trick and solution, and those who where annoyed over the whole course of the novel because the characters were making a fuss over something so obvious. As I said, I kind of was lucky enough to be pleasantly surprised with the solution, but I think even if I arrived at the precise method and arrived at the solution myself I still would have liked the trick just as in Ayatsuji's novel.
Even if the trick does not surprise you, this third novel fortunately improved from the last one (which was initially written as the first in the series) so that it resembles Mori's debut work in terms of dialogue, themes and unexpected endings. The finale really was unforgettable due to its lasting uncertainty concerning the motive and the uncanny genius. Mori's stories need some time to develop. You have to endure the horrible exposition in the beginning (his debut work starts out awesome though) but if it goes on like this I can look forward to more overall good novels in this series.