Who slipped something into veteran CNN reporter Dan McLean's soup that made one of his most memorable dinners--the star- studded annual banquet of the White House Correspondents Association--his last? Before you answer, you may want to know that (1) right-wing radio ranter Jerry Knight thinks the murder is part of a botched liberal plot to assassinate another guest, inoffensive conservative President Dale Hammond; (2) Jerry's opposite number, Kennedy-loving Washington Post reporter Jane Day, is convinced McLean was killed to prevent him from going public with a scandalous story dating back to the US evacuation from Vietnam; (3) an amateur videotape captured an image of the Vietnamese poisoner, whose corpse D.C. cop A.L. Jones will soon be called upon to identify; (4) the First Lady, a hard-charging hacker who investigates on her own, comes to suspect the President himself; and (5) none of this matters: A portentous finale at the Vietnam Memorial will reveal that everybody's wrong--all the mystery-mongering is smoke and red herrings, and the killer is nobody you care about. Not that that clue helps to distinguish the perp from the rest of the famous, forgettable cast. Buckets of empty vivacity as Jerry and Jane (Knight and Day, 1995), probably uneasy at being becalmed in such underplotted folderol, volley toothless partisan insults. An early front- runner for the title of the year's most disposable mystery.