In the near future, a mysterious alien artifact (reminiscent of that in "2001") is discovered on the ocean floor. Hoping for material gain, a secret team is assembled to 'salvage' it and investigate it. But the egg-shaped item is impervious to all attempts to mess with it.
Meanwhile, two alien beings are on Earth - and have been for untold time, changing their shape, way of being - and largely unaware of who and what they are. What is their connection to the artifact? And why are drawn to each other in what seems must be a confrontation that will wipe one or the other out?
A very 'mainstream thriller' feel to this novel; it's enjoyable but not extremely memorable. Haldeman's good, but this isn't one of his standout books.