The Dark Frontier is the debut novel of Eric Ambler, who contributed so much to the espionage and crime genres through such marvelous books as Background to Danger, Epitaph for a Spy, Cause for Alarm, A Coffin for Dimitrios, and Journey into Fear. Written in 1936, it was not published in the United States for several decades. The book varies quite a lot from the rest of his work, and will be less satisfying to almost any reader. Serious Ambler fans, however, would be making a mistake if they passed up this book. Seeing this effort will help them appreciate the mature Ambler talent even more.