Wiseguy - Season 4 - Eps 1: Fruit of the Poisonous Tree (1)
While Frank is in Washington to talk to Paul about returning to work, Dan calls to say Vinnie missed his last check-in. Frank goes to Vinnie's house and finds evidence that he was kidnapped. Despite Paul's objections, Frank begins his own investigation, finding out from Carlotta that Vinnie was looking into the death of a priest in El Salvador. Frank follows the trail to Miami and Michael Santana, a disbarred Federal prosecutor, and the last person Vinnie contacted. Santana refuses to help Frank, saying he doesn't know anything about Vinnie's disappearance. Digging deeper, Frank stumbles upon a CIA investigation and is ordered to back off. (source: http://www.plasticcow.com/wiseguy)
About Wiseguy

Title: Wiseguy
First Air Date: 1987-09-16
Last Air Date: 1990-12-22
Status: Ended
Rating: 6.5/10 (from 31 votes)
Language: EN
Seasons: 5
Total Episodes: 75
Network: CBS
Genres: Crime, Drama, Action & Adventure
Production Companies: Stephen J. Cannell Productions
Synopsis
Vinnie Terranova does time in a New Jersey penitentiary to set up his undercover role as an agent for the OCB (Organized Crime Bureau) of the United States. His roots in a traditional Italian city neighborhood form the underlying dramatic base throughout the series, bringing him into conflict with his conservative mother and other family members while acting undercover as syndicate enforcer.
Cast

Steven Bauer
Michael Santana

Jonathan Banks
Frank McPike

Jim Byrnes
Daniel Benjamin 'Lifeguard' Burroughs

Cecil Hoffman
Hillary Stein

Maximilian Schell
Amado Guzman