The Cat Who Saw Stars by Lilian Jackson Braun

UFOs in Mooseville? Rumors abound that a missing backpacker has been abducted, and it looks like Jim Qwilleran’s sedate summer may be interrupted by an investigation — with the help of his own little aliens, Koko and Yum Yum. And when the backpacker’s body turns up — and transplanted Floridian Owen Bowen is found dead soon afterward — the search for intelligent life turns into a close encounter with a killer…