A Superior Death by Nevada Barr (Anna Pigeon #2, Very good, 1995, Pbk, 373 pages, Avon Books)

The inaccessible wreck, Kamloops, has rested at the bottom of Lake Superior for nearly seven decades, the bodies of its ill-fated crew eerily preserved in the frigid waters. But now there is an extra corpse on board -- a newly slain interloper suspiciously dressed in 1920's clothing. It is Anna Pigeon's job as a ranger with the U.S. National Park Service to help protect wild and lonely places from civilization's corrupting touch. Now a bizarre mystery held firmly in a Great Lake's icy grip is drawing Anna into a nightmare of greed and cold-blooded murder. And what she finds waiting beneath the surface could prove fatal.