Murder for Lunch — Haughton Murphy

When Reuben Frost's old firm is faced with murder, the Wall Street legend comes out of retirement to find the killer
 
No one on Park Avenue can hail a taxi quite like Graham Donovan. He stands outside his apartment building, arm outstretched like a true master of the universe. Today, he rides downtown with the Wall StreetJournal on his lap, his mind preoccupied by rumors that his venerable Wall Street law firm, Chase & Ward, is about to be accused of insider trading. A suspicious letter has surfaced bearing Donovan's signature, and he's desperate to protect his reputation. But in the end, it doesn't matter, for he has hailed his final cab.
 
When Donovan drops dead during lunch, the firm calls on its greatest mind, seventy-four-year-old Reuben Frost, a brilliant lawyer who was recently forced into retirement. It's clear Donovan has been poisoned, but by who? Only Frost knows the ins and outs of Wall Street well enough to pinpoint the killer.
 
Murder for Lunch is the 1st book in the Reuben Frost Mysteries, but you may enjoy reading the series in any order.