SOUTH OF HELL Dig up the past. Pay the price.    With one phone call from a man he barely recalls meeting years ago, South Florida detective Louis Kincaid heads to the Michigan town of his college days to reopen a disturbing cold case -- and finds himself confronting his own painful past secrets...secrets that risk his future with the woman he loves, detective Joe Frye.   Ann Arbor police detective Jake Shockey wants Kincaid's help in the case of Jean Brandt, who went missing nine years ago -- and whose husband, Owen, has since been paroled. Now, Owen Brandt's girlfriend appears to be at risk, and Shockey is desperate to get involved. Kincaid soon unearths the deeply personal reasons why...and with Joe Frye assisting, Kincaid links yesterday's jealousies with today's potentially lethal vengeance. It's only a matter of time before one will win out over the other -- and before Kincaid's own shattering revelations will be forced out into the light of day.