They Walked Like Men

Novel, first published: Doubleday 1962

The novel follows the format of a thriller, and Simak brings back his newspaperman hero to solve the mystery. In the first chapter, the newsman is nearly caught in a vicious human-trap, actually one of the shape-changing aliens, who naturally look like black bowling balls. ...
The reporter, with the help of his girl friend, tumbles on to the aliens' scheme to send the world into economic chaos: if aliens own all the property and property rights vanish, it will be an end to jobs, credit, and business - and, of course, to the hopes and dreams of humanity.
The aliens are succeeding because of their incredible metamorphic ability - they change into such exact replicas of humans that no one can tell the difference. They are totally unfeeling galactic realtors, buying and selling planets, unconcerned about the races inhabiting them. Nobody will believe in such an invasion, and the situation looks hopeless until the newsman hero discovers that the odor of skunks distracts the aliens like sex does for humans. The news hawk sniffs out Windy, an old skunk handler and one of Simak's unlikely saviors of the human race, who rounds up enough skunks to halt the invasion.

Ewald, Robert J.: When the Fires Burn High and the Wind is from the North, p.78-79