It's 1945, and the focus of this readable and absorbing first thriller is a Nazi commando in the US with direct orders from Hitler to assassinate President Roosevelt. Variations of this story have been told before, of course, whether the intended victim was de Gaulle or Churchill or the president. We know the effort doesn't succeed, so the trick lies in the telling: Why does the villain fail? Former newsman Davis keeps the reader guessing about that with a few nifty twists. William Miller (nÇ Wilhelm Mueller) is a most competent agent, rapidly insinuating himself into the populace of Warm Springs, Ga., FDR's popular retreat, and putting into place a well-designed plan that will draw FDR into a death trap. When the OSS learns of the plot, the only man in the U.S. intelligence community who can identify Mueller is young officer Jack Cole, whom Mueller shot and left for dead in a Belgian forest during a brutal massacre of captured American troops. Cole is a relatively bland character compared to the would-be killer, who's human enough almost to decide to turn his back on his mission--until the firebombing of Dresden, which kills his mother, strengthens his resolve. But Cole's story is fascinating because of the self-serving efforts of J. Edgar Hoover to promote the FBI, even if it means risking the president's life. This subplot ties in nicely with Davis's neatest touch: Rather than acting solely alone, Mueller is supported by a pair of fellow spies, in place for years, who implement several false attacks that lead the Secret Service virtually to deliver the president to his killer. Many readers may anticipate the final surprise, but few will be disappointed by this engrossing read. Very plausible, very possible, and very well done.