On an early August morning in Harney County, Florida, fanatic bass fisherman Robert Clinch takes his bass boat out onto the lake. A few hours later, he is found floating dead in that same lake.
Private investigator R.J. Decker is hired by sugar cane tycoon Dennis Gault, another fanatic bass fisherman, to prove that celebrity fisherman Richard "Dickie" Lockhart, Gault's main rival on the fishing tournament circuit, is a cheat.
Decker, an expert photographer, used to work for a newspaper, but was fired, and served a short prison sentence, after assaulting a teenaged kid trying to steal camera equipment out of his car (his ex-wife, Catherine, playfully nicknamed him "Rage" on account of his temper).
Investigating Lockhart's hometown in Harney County, Florida, Decker looks up an old newspaper friend, a laconic reporter named Ott Pickney. Finding the local bass fishing guides too expensive, Decker takes Ott's advice and meets a reclusive hermit who lives in the woods, calling himself "Skink." While teaching Decker about fishing, he mentions seeing Bobby Clinch on the lake on the morning he died. The strange thing is, he wasn't fishing.
Attending Bobby's funeral, Decker meets Elaine "Lanie" Gault, Dennis's sister, a former fashion model who confides to Decker that she and Bobby were lovers. She tells Decker that Dennis hired Bobby to catch Lockhart first, only she believes Lockhart had Bobby killed.
When Decker mentions her suspicions to Ott, Ott is skeptical and dismissive; the coroner ruled Bobby Clinch's death an accident (the result of a crash while joyriding) and besides, a murder over fishing is too outlandish to be believed. However, when Ott interviews Bobby's widow, he also discovers clues that Bobby wasn't fishing. Tracking down the junked remains of his boat, Ott discovers signs of sabotage. Unfortunately, at that moment he is tracked down and murdered.
After finding his body, Skink and Decker are both committed to nailing the likely culprit, Dickie Lockhart. They tail Lockhart to his latest fishing tournament, on Lake Maurepas in Louisiana, but inadvertently photograph the wrong gang of cheaters, and Lockhart wins the tournament anyway.
Decker is dispirited, but Skink tells him not to worry, adding, "worse comes to worst, I'll just shoot the fucker," to Decker's alarm. Later, he returns to their hotel room and finds Lanie waiting for him. They sleep together, but after her drops her off at her hotel, he notices lights on at the lakeside. Going to investigate, he finds Dickie Lockhart floating in the weigh tank, clubbed to death.
Assuming Skink is the culprit, Decker quickly and quietly leaves Louisiana and drives back to Florida. But when he returns home, he finds the Miami police, led by Detective Al Garcia, waiting for him. Skink intercepts Decker and tells him the bad news: Decker has been framed. The whole assignment from Gault was a set-up, allowing Gault to kill his hated rival and put the blame on Decker.
Meanwhile, Lockhart's corporate sponsors, the mammoth Outdoor Christian Network, led by TV evangelist Reverend Charles "Charlie" Weeb, loses no time in announcing a Lockhart memorial fishing tournament, a publicity stunt to boost sales at "Lunker Lakes", a massive housing development built by Weeb on the very edge of the Everglades, targeted almost exclusively at bass fishing enthusiasts.
In reality, advance sales of the condominia at Lunker Lakes have been going very slowly, and Reverend Weeb is becoming increasingly desperate, as the Outdoor Christian Network has so much money sunk into the project that its failure will mean his own financial ruin. He becomes even more desperate when the bass salted into the "lakes" (shallow, narrow, canals) die, revealing that the water is toxic (in his haste to build his "dream city," Weeb neglected to learn that Lunker Lakes occupies the site of a former landfill).
While trying to escape Miami, Decker and Skink are stopped by Miami Police Detective Al Garcia, a friend of Decker's. Garcia has already interviewed Gault, picking numerous holes in his frame-up story, and is more than ready to believe Decker's version of events. Meanwhile, a worried Gault sends his hired thug, Thomas Curl, to track down Decker and kill him before Garcia finds him.
While researching Lockhart's history, Decker and Skink learn of the housing development, and Skink is determined to stop it by sabotaging the fishing tournament. With the help of Skink's friend, State Trooper Jim Tile, Decker tracks down Lanie at her beachfront condominium and forces her to confess, on tape, that she helped her brother frame Decker for Lockhart's murder. Lanie admits that she first became involved with Decker at Dennis's suggestion, to help punish Lockhart for Bobby Clinch's murder. After Lockhart was killed, Dennis warned her that he might be a suspect in the murder, so he convinced Lanie to give a statement to the police, falsely claiming that Decker was on his way to see Lockhart when she last saw him. For all her beautiful looks and her skill at handling men, Lanie was too dim-witted to realize that Dennis killed both Bobby and Lockhart, and that she was effectively "whoring for [her] own brother." Lanie's recorded statement is enough to clear Decker's name, assuming Curl doesn't kill him first.
Unfortunately, Curl kidnaps Catherine, Decker's ex-wife, with whom he is still in love, and demands that Decker trade his life for hers. Decker tells Skink to go ahead with his plan to sabotage the tournament, Decker will deal with Curl himself.
The "secret weapon" of Skink's plan is his "partner," a gargantuan bass named "Queenie," who Skink has raised in secret behind his cabin, and, at 29 pounds even, is easily the largest bass in the world. Skink's original plan is to have Jim Tile and Al Garcia enter the tournament, posing as brothers, and win by catching Queenie. With publicity for Lunker Lakes homes aimed exclusively at white people, Skink predicts that having an African-American and a Cuban featured on national television as the winners of the tournament will be fatal for sales.