One of the most sinister exchanges in the Niira Radia tapes takes place past 11 pm on June 10, 2009. The then PR diva is having a tense conversation with Manoj Modi, the right-hand man of India’s most powerful businessman, Mukesh Ambani. The top management of conglomerate Reliance Industries—a client of Radia’s PR firm—is upset, very upset. Business magazine Forbes India (published by the then Raghav Bahl-promoted Network 18) had committed, according to the Ambanis, a grave transgression. An irreverent column on the rich and famous, which went by the moniker Insnider, had taken a light-hearted swipe at the children of the RIL chairman.

Radia is trying to secure an apology from the Forbes editors. But Manoj Modi is in no mood for a mere apology. He threatens to press criminal charges on the then editor...