Based on the novel by James Herbert, "Fluke" faces an uphill battle: It's too dark a story for children, and its earnest but corny underpinnings will bore adults. Matthew Modine stars and voices as a driven businessman who dies and is reincarnated as a dog. Troubling dreams from his human past propel the pooch on a journey to find the home of his former wife (Nancy Travis) and young son ("Searching for Bobby Fischer's" Max Pomeranc), in the conviction that they are in danger. This plot-pusher, however, turns out to be a red herring. "Flight of the Innocent," the Italian-born director's first film, married an emotional story to highly imaginative, even magical visuals; it swept the viewer along. "Fluke" lacks a similar lyricism. Although the story obviously holds a great resonance for Carlei, moviegoers not already disposed to his spiritual beliefs will be left shaking their heads. Starring Matthew Modine, Nancy Travis and Eric Stoltz. Directed by Carlo Carlei. Written by Carlo Carlei and James Carrington. Produced by Paul Maslansky and Lata Ryan. An MGM release. Fantasy. Rated PG for a dog attack and a disturbing car crash. Running time: 96 min.