A question not directly related to Glen Cook: My brother is asking for help in identifying a book he read years ago: It's hard SF of the space-battle variety, akin in spirit to "Passage at Arms" (which is why I thought of this list as a possible source for someone who might recognize the book). They key point my brother recalls is that of a warship in interstellar flight seeing a mysterious "shadow" on its sensor screen. The ship's officers can't tell if it's an equipment glitch or an actual enemy; it appears to move with them as if it's tracking them, but maybe it's an artifact of equipment failure. As the plot develops, it turns out it's an actual enemy ship. And that's all I can tell you about the book. Anyone recognize this trope? Steve/Stacey