An overwhelming fog obscures a killer in this Captain Heimrich whodunit from the authors of the "excellent" Mr. and Mrs. North Mysteries (TheNew Yorker).   Capt. M. L. Heimrich of the New York State Police may not have the flash of hard-boiled city detectives, but there's no lead the intrepid investigator won't follow until his every hunch is satisfied . . .   Those of lesser means would jump at the chance to live in a grand estate like High Ridge. But in the dense January fog, the Bromwell family's mansion becomes home to a dastardly murder that shocks the whole of Westchester County.   When Captain Heimrich is called in to solve the case, he quickly realizes the task set before him won't be easy. The timeline of Marta Bromwell's death is hazy, and the suspects are many. There's the mousy secretary, the indifferent mother-in-law, the motorist with a convenient flat tire, and a thief brazen enough to steal a Cadillac with a fortune in gems stashed in the glove box.   Heimrich knows the obvious answer isn't always the right one, but as he digs into the Bromwells' secrets, someone else in the house is murdered. Now he'll have to catch a killer hiding right under his nose . . .   Foggy, Foggy Death is the 3rd book in the Captain Heimrich Mysteries, but you may enjoy reading the series in any order.