Pluto.

PREVIOUS BOOK IN SERIES: NEPTUNE, ISBN 9781250296627. Hugo Award winner Ben Bova and Les Johnson complete Bova's Outer Planets series, a Grand Tour ( Uranus, Neptune, and Pluto ) of the human settled solar system, with a final encounter on Pluto. Major Larry Randall has been called to Pluto to retrieve Dr. Aaron Mikelson. Mikelson, no longer human after a horrific accident, is now melded to an AI. His enhanced senses have detected an alien a...