The Power of Five (also known as The Gatekeepers in the US) is a series of five fantasy and suspense novels, written by English author Anthony Horowitz and 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. The series is published in the United Kingdom by Walker Books Ltd and in the United States by Scholastic Press.