The Longer the Thread — Emma Lathen

Corpses certainly are bad for business...
as John Putnam Thatcher, senior vice-president of the Sloan Guaranty Trust, found out when he investigated the affairs of Slax Unlimited. Slax, a garment-manufacturing firm, had recently opened a Sloan-backed plant in Puerto Rico--and now the plant was beset with some very suspicious "accidents."

Foreman Benito Dominguez was a prime suspect for sabotage. So was Prudencio Nadal, the student leftist leader who was calling on plant workers to strike. With the situation deteriorating and three million dollars of Sloan money at stake, there was nothing for Thatcher to do but go down to San Juan and investigate.

What he found was a body in the front office, violence in a fiery festival, and a ransom not to the governor of Puerto Rico. When another body turned up, Thatcher himself set off in search of the murder. He had, after all, an investment to protect!