The Power of Five (re-titled as The Gatekeepers in the US) is a series of five fantasy and suspense novels, written by English author Anthony Horowitz. Published between 2005 and 2012, it is an updated re-imagining of Horowitz's Pentagram series, which the author had left unfinished in the 1980s after he only wrote four of the five planned books in the series. The novels deal heavily in the occult and examples of things such as human sacrifice and blood rituals are major plot elements, such as in the first book, where Matthew Freeman is hunted by a Cult who want to conduct a blood sacrifice on him to blast open a portal using a combination of nuclear physics and black magic, to unlock another dimension which is holding a group of ancient evil demons captive. The series is published in the United Kingdom by Walker Books Ltd and in the United States by Scholastic Press. Source: Wikipedia (en)