Vigilant is a science fiction novel written by the Canadian author James Alan Gardner, published in 1999 by HarperCollins Publishers under its various imprints.HarperCollins, Avon, SFBC/Avon-Eos; paperback edition 1999, Eos Books. The book is the third volume in Gardner's League of Peoples series, after Expendable (1997) and Commitment Hour (1998).The series continues through Hunted (2000), Ascending (2001), Trapped (2002), and Radiant (2004).