According to Henry, why is the taxidermist's story suspicious?

The content of the taxidermist’s story leads Henry to the suspicion that the taxidermist was, in fact, involved in the sorts of atrocities that he is writing about. At around the same time, Henry’s dog acquires rabies and attacks his cat, with the result that both animals are put down. The juxtaposition of these events, with their associated intensities of emotion, leads Henry into a confrontation with the taxidermist, who offers Henry more scenes from his play to consider. These scenes confirm Henry’s suspicions, and the confrontation escalates to the point where the taxidermist stabs Henry.