The poetic meter creeps up on you. It's not there at all in the first paragraph, but by the time Aloysius enters the club, it's undeniable, and it gets stronger from there. The slow transition perfectly matches Aloysius' transformation. I love that the reader never knows for sure if he's a literal werewolf or if he's only figuratively transformed during his periodic forays into this other life of his.
On a technical note, I'd describe the meter as a double dactylic tetrameter. That is, each line is a pair of four beat phrases, where each beat is a triplet (strong-weak-weak or short-long). As the story builds, the meter becomes more pronounced AND each pair of phrases become more clearly related or complementary (think Beowulf, or the Psalms).
All in all, beautifully done.