Tomorrow, ProPublica and PBS FRONTLINE will publish the results of a months-long investigation into how David Coleman Headley worked as a spy for the Pakistan’s Inter-Services Intelligence Directorate (ISI) while planning the 2008 Mumbai attack for the terrorist organization Lashkar-i-Taiba. In spite of this information, Pakistan has not arrested an ISI officer or other accused masterminds of the Mumbai plot who have been indicted by the U.S. Six Americans were among the 166 people killed in the three-day siege.

In a preview interview today, Fresh Air’s Terry Gross talks to ProPublica’s Sebastian Rotella about the investigation. They will discuss Headley’s role as an informant for the DEA, how U.S. intelligence agencies and law enforcement officials responded to repeated warnings about Headley’s activities and ultimately, as some Indian officials believe, whether Headley was a double agent.

Interviews with Rotella and/or FRONTLINE producer Tom Jennings will also air on the Bob Edwards Show The Takeaway and The World tomorrow. Jennings and Rotella will also participate in a chat on Wednesday at 11 a.m. Eastern to answer any questions you may have about the reports.

The investigation will be published on our website tomorrow morning, and the PBS FRONTLINE episode will air tomorrow night. You can watch a preview below and check here for your local listings.