Accounting for Clues is a murder mystery involving former private investigator and CPA Claude Monday. He is asked to assist police in a case where a serial killer mails accounting statements to police then leaves a copy at the crime scene.
The story unfolds in shifting perspective, from Claude's viewpoint to the killer's, who is trying to cope with his wife's miscarriage and succeeding illness as well as his own failures.
Despite concerns from Claude's wife, Kay, that he might get too involved, Claude works the case. Gradually, he gets so into it he does not notice his wife's call when the couple's eighteen-year-old, Nicole, is hospitalized.
Claude eventually solves the meaning of the statements. Later, Nicole goes out with friends, informing her dad where she’s going. Claude, too wrapped up in his thoughts upon decoding the clues, doesn’t hear her. Before leaving, Nicole hands the mail to Claude, who notices an envelope with no return address or stamp, wondering how it got delivered. Upon opening it, he discovers it’s the killer’s clue and theorizes the guy knows where he lives, even had the nerve to deliver the clue. Claude then solves this clue—and realizes the next victim to be his daughter.
During his frantic search, he finds Nicole's car. Though abandoned, a clue is left in the car’s trunk, this one hinting where the suspect has taken the girl. Claude calls police and, unsure how quickly they’ll arrive at the scene in addition to feeling responsible for Nicole’s predicament, goes there himself.
At the location, he finds the place unoccupied then hears a car drive off and deduces who’s in the vehicle: the killer and Nicole.
The guy tells Nicole, now bound and gagged, he will dump her in the nearby river then take care of Claude. However, as they approach the river, the girl loosens her bonds, distracting her captor. As a result, he swerves and crashes into the water.
Tailing them, Claude jumps into the river, swims to the car and grasps his daughter's hand. But after swimming ashore, he discovers it's the killer he's pulled free.
After a struggle, Claude subdues the man then rescues Nicole and takes her to the hospital. Kay joins them in the Intensive Care Unit, father and daughter with minor injuries. Claude promises this to be his last case and the couple reconciles, again a family.