LETTERS TO MY READERS - MaryJanice Davidson. It was Professor Tanten who did it, in the ballroom, with a martini shaker... Aspiring mystery writer Caro Swenson can see that: Professor Tanten is standing there, covered in blood. But where's the body - or bodies? Six people are missing from the mystery weekend, and Caro's on the case with a hot-but-possibly homicidal hunk who seems to want to get his hands on Caro's...clues. SINGLE WHITE DEAD GUY -...