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.
Vinnie (Ken Wahl) is released from prison where he has been for two years to establish his cover. He meets his boss, Frank McPike (Jonathan Banks) and gets to see his coach and mentor, Jerry Greco (Robert Miranda). Greco is killed and Vinnie demands to be put in to finish the investigation. He uses his ingenuity to get a foothold in the Steelgrave crime family, but it will take a while to finish this job.
Vinnie and Sonny's right hand man, Tony Grecco, have a run-in with the cops for which Vinnie is arrested. The Steelgraves find that guns are being exported illegally using their pier and decide to take possession of the guns and sell them back to the owner. The meeting goes down bad and ends with Dave Steelgrave's death. Vinnie gets rid of Tony by setting him up and having him arrested. To prove his loyalty, Vinnie shoots a federal agent for Sonny (The fed was warned and wore a bullet proof vest and was then moved out of state).
After ""making his bones"", Vinnie moves up in the Steelgrave family when Sonny gives him Tony's old waterfront action. The pressure is on Sonny when ""Pat the Cat"" Patrice insists on installing accountant Sid Royce in the office to keep an eye on his interests, and to balance the power, Philly's ""No Money"" Mahoney insists Sonny find a place for his man, Harry ""the Hunch"". And, as if he doesn't have enough to worry about, there's a new district attorney who plans to make a name for himself by bringing Sonny down. Sonny and Vinnie are arrested for attempted murder when someone shoots at the DA and throws the gun to Sonny. (source: http://www.plasticcow.com/wiseguy)
While trying to regain control over the men running his ghetto drug operation, Sonny gets a call from Italy asking him to take in his nephew and teach him the business. After getting into a fight with Lorenzo, Vinnie has Frank do a check and it turns out the guy is really an insane mass murderer who killed the real Lorenzo before coming to the States. Frank and Pete both warn Vinnie to break off his budding romance with Gina, the widow of a crooked cop who killed himself. Vinnie and Lorenzo have a showdown after Lorenzo rapes Gina, ending with Vinnie killing him. (source: http://www.plasticcow.com/wiseguy)
Vinnie nearly blows his cover when he becomes obsessed with finding out who killed his cousin, causing Frank to threaten him with dismissal. Frank desperately wants Vinnie to concentrate on nailing the Zaratzos, who are trying to arrange a drug smuggling deal with Sonny, because they killed one of Frank's agents.
After several deals go sour, Sonny starts suspecting Vinnie may be a plant. Frank orders Vinnie to drop the case when he finds out the local police have an informer in Sonny's operations. Sid has Frank picked up and tortured, but Vinnie and undercover cop Karen Malloy rescue him. Karen's disappearance points the finger at Sid as the leak.
Vinnie decides he must tell his mother the truth about his work when she is hospitalized after being mugged. Frank has Lifeguard bug Carlotta's hospital room, then has a change of heart when Carlotta charms Sonny by telling him how much Vinnie loves him. Vinnie's admiration for Sonny lessens when his own informal investigation into his mother's mugging leads directly back to Sonny's empire. (source: http://www.plasticcow.com/wiseguy)
When Sonny refuses to let Joey out of his contract, the singer goes to Mahoney to ask him to speak on his behalf. Mahoney tells Sonny he's losing his power, so Sonny has two crooked cops rough Joey up, unaware that one of them is a loose cannon who crushes the singer's voice box. After Frank interrogates them, the cops follow Frank and get pictures of him meeting with Vinnie, which they plan to sell to Sonny. Since Vinnie is now acting as Sonny's ""right hand"", Joey Bags insists that he be formally initiated into la famiglia. A confrontation between Joey, the cops and the mob bosses ends up with Joey and the cops dead, and Frank switching the photo of him and Vinnie with one showing him meeting with Patrice. (source:http://www.plasticcow.com/wiseguy)
A staged argument between Sonny and Vinnie prompts Patrice to propose that Vinnie leave Sonny and come to work for him. Sonny is busy planning his wedding to Theresa while keeping an eye on the growing power struggle between him and Patrice. After Patrice tells Vinnie he's going to hit Sonny in the morning, Vinnie arranges for Frank to arrive before the scheduled time to make the arrests. Sonny kills Patrice at his bachelor party, then demands to know why Vinnie didn't tell him about the hit. (source: http://www.plasticcow.com/wiseguy)
While Vinnie tries to reassure Sonny of his loyalty, Aldo calls to warn Sonny the cops are on the way, causing Sonny to flee, with Vinnie right behind him. They end up locked in a closed theater where they fight, drink and try to justify their lives. Meanwhile, Frank is distraught over Vinnie's disappearance as he tries to get information from the other mob bosses. After he finds out Vinnie's location, he arranges a rescue, which culminates in Sonny committing suicide and Vinnie being arrested to protect his cover. (source: http://www.plasticcow.com/wiseguy)
Distraught over the guilt he feels over Sonny's death, Vinnie is ordered into therapy. Pete hears the confession of a man with a contract out on his life, and is torn between his vows and giving Vinnie the information he needs to help the guy out. (source: http://www.plasticcow.com/wiseguy)
Frank wants to get Vinnie back on the job, so he assigns him to a routine case investigating hit man Roger Lococco, unknowingly dropping Vinnie into the middle of a case that has international repercussions. After winning Roger's confidence, Vinnie is asked to work for Mel and Susan Profitt, a brother and sister team who run a worldwide drugs and munitions organization. (source: http://www.plasticcow.com/wiseguy)
Convinced an associate's bride-to-be is a Fed, Mel insists he postpone the wedding. Insulted, Paco brings up a death squad to hit Mel, then arranges to kidnap Susan to force Mel to give him all of their drug action. Vinnie and Roger rescue Susan. Frank finds out Paco's bride was an undercover CIA agent. (source: http://www.plasticcow.com/wiseguy)
Vinnie has second thoughts about the case and tells Frank he wants out. When he goes to Mel to resign, Mel offers him a chance to take over his worldwide drug operation. The catch: Vinnie must go to Tennessee and take it back from the middle men who have seized control. (source: http://www.plasticcow.com/wiseguy)
Mel's desire to buy a baseball franchise is two-fold: he wants to play on it, and he wants to take it away from an old business associate who cheated him in a Mexican drug deal. Vinnie is fighting his growing feelings for Susan while trying to discourage Jacqueline from getting reinvolved with all the debauchery on the Hotei. (source: http://www.plasticcow.com/wiseguy)
When some of his munitions contacts begin drying up, Mel decides to blackmail a French Deputy Minister of Defense into supplying him with the weapons he needs. After setting Vinnie up to be arrested for espionage, Susan makes it up to him by letting him go to bed with her. When Vinnie mysteriously comes up with the documents Mel needs, he arouses Roger's suspicions. (source: http://www.plasticcow.com/wiseguy)
Hiding out in Vancouver after the fall of the Steelgrave empire, Aldo Baglia sees a photo of Vinnie in the paper and decides to even the score, sending Vinnie into a coma from two serious gunshot wounds. Roger, using his CIA contact, tracks down Aldo, but Aldo accidentally falls off the roof of a building before he can answer any questions. Upset about Vinnie being shot and his wife leaving him, Frank falls into the arms of a pretty CIA agent. (source: http://www.plasticcow.com/wiseguy)
After his munitions operation starts falling apart, Mel orders Vinnie to set up a meet with the mob to use his immense cocaine trade to regain financial power. Still suspicious of Vinnie, Roger has Herb check him out and learns that Vinnie is working for the OCB. Vinnie takes Mel to Don Aiuppo, who arranges for the drug trafficking to be overseen by two ""third generation"" gangsters who will stop at nothing, including threatening Carlotta, to insure the deal doesn't fall through. (source: http://www.plasticcow.com/wiseguy)
With Herb becoming more insistent about their agenda, Roger schemes to get Mel to fund the military coup of Isle Pavot. Unfortunately, Mel is convinced that Cabra, the man Herb wants to put into power, has put a voodoo curse on him and orders Vinnie to find a woman who can remove the curse. Realizing that Mel is a major stumbling block to the mission, Roger sends him over the edge by smashing the crystal that contains Mel's soul. Despondent, Mel asks Susan to kill him, and she does. (source: http://www.plasticcow.com/wiseguy)
Susan is arrested for Mel's murder and while she's in jail, she tells Vinnie she's pregnant with their baby. Roger sets Vinnie up for Mel's murder, then sets about driving Susan mad so he can gain control of her vast fortune to fund the Isle Pavot coup. Frank trails Roger to Herb. Vinnie finds out Susan isn't pregnant. Susan goes insane and has to be institutionalized. (source: http://www.plasticcow.com/wiseguy)
With Mel and Susan out of the picture, Frank considers the case closed. However, Vinnie wants to find out where Roger fits into it all and goes to Vancouver to find him, but instead, he witnesses Preet's murder and links it to Herb. Frank and Vinnie go to Stockton, where Roger is training mercenaries for the coup. Roger kidnaps Frank and tells Vinnie he'll be released after the operation, then Vinnie tells Roger that Herb is using him. Roger overhears Lelond assuring a major corporation that they can get all the cheap labor they need once he takes over Isle Pavot and realizes the coup is just an excuse for Herb to regain acceptance in Washington. Roger works with Frank and Vinnie to set up Herb and sabotage the coup. (source: http://www.plasticcow.com/wiseguy)
Vinnie and Roger are subpoenaed to testify at a Senate hearing concerning Ketcher and the failed overthrow of Isle Pavot, but Vinnie balks at McPike's orders that he testify as a hood and not as an OCB agent. Roger testifies, then demands to be released from protective custody after an attempt on his life. When Roger is killed in a mysterious boat explosion, Vinnie testifies anonymously and substantiates Roger's testimony that Herb was responsible for everything. Abandoned by everyone in Washington, Herb is approached by the Soviet Union to defect, but he kills himself instead. Tired of all the lies, Vinnie resigns from the OCB. Roger ""reappears"" to let Vinnie know he faked his own death to escape the CIA. (source: http://www.plasticcow.com/wiseguy)