. . "San Francisco (Calif.)" . . . . "Mystery fiction" . . . "Double or nothing" . "Fiction" . . . . . . "Minnesota nurse Ellen Merchand and her sister Claire have arranged for a house exchange with a San Francisco art dealer. What the sisters don't know is that Herb Carmody plans to use the house exchange as an alibi for his wife's murder. Then there is Sid Balzarian, a small-time criminal with plans to kidnap Jane Carmody." . . .