On a gloomy New Year's Eve, recently bereft of wife and partner, down-and-out New York City PI John Justin Mallory is hired by Mrgenstrm, a little green elf who wants Mallory to track down a stolen unicorn. After gradually accepting that his client is not an alcohol-fueled hallucination, Mallory deftly takes on a shadow city of demons, leprechauns and gnomes even as he learns that his own future hinges on the unicorn's recovery.