A Gathering of Widowmakers (Widowmaker Series #4)

Jefferson Nighthawk, the original Widowmaker, has retired to an obscure little planet, content that his two clones can handle any problems that arise -- until the day the two clones meet on opposite sides, and the original must come out of retirement to make peace, because there is a threat on the horizon that will require the combined skills and might of all three Widowmakers.