He often met with Nick Sobotka, who frequently served as Frank's go-between, and Vondas took an almost paternal interest in the younger man. Impressed with Nick's intelligence, he gave him the task of stealing a shipment of chemicals. He intervened in a dispute over a debt between Nick's cousin Ziggy Sobotka and a drug dealer supplied by the Greek, Melvin "Cheese" Wagstaff. Despite a personal dislike for Ziggy he ordered Serge to argue his case to Proposition Joe, Cheese's uncle and superior. Vondas' distrust of Ziggy proved correct when Ziggy killed Glekas in an argument over payment for stolen goods. Ziggy was arrested soon afterwards and Vondas distanced the murder from the rest of the operation by removing all evidence of the business from the warehouse.
When Lieutenant Daniels's port detail began investigating the Greek's activity Frank Sobotka realized and tipped Vondas. During the finale outset's of the investigation, the detail finally got a photo of Spiros when he was meeting drug lieutenant Eton on the waterfront of Baltimore. The detail then surveilled his home and followed him to meetings at hotel rooms and the diner where he met with associates.
The Greek ordered Vondas to shut down the smuggling temporarily and replaced all of his personnel's telephones. The Greek withdrew from their meeting place at the cafe and began meeting Vondas in hotel rooms.
When the detail began rounding up the members of the Greek's smuggling ring, they held off on Vondas as they felt he could lead them to the Greek. When Sobotka was arrested Vondas suggested that they could broker his loyalty by having a witness against Ziggy change his story. He put the proposition to Frank through Nick. Frank had already agreed to testify against the Greek's crew, but decided to meet with them for Ziggy's sake. The Greek learned of Frank's agreement through his inside man at the FBI, agent Koutris, and had Vondas murder Frank.
Following the murder Vondas left the country under a fake passport with the Greek, using the alias Kirko Skaddeng. Before Vondas left he met with Proposition Joe to assure him that the Greek's operation would continue to supply him using new personnel after a short break to avoid the investigation.
Marlo once again meets with Vondas, and attempts to sell himself as an insurance policy for the Greeks, implying that if something were to happen to Proposition Joe, they would need another agent they could do business with. While Vondas believes that all that matters is that the Greeks already have a secure relationship with someone they trust, The Greek states that Marlo makes a valid point that it is wise to have an insurance policy in volatile times, implicitly telling Marlo that if he moves on Joe, they will not stop him. After Marlo leaves, Vondas and the Greek seem resigned to Joe's demise and to initiating a new business relationship with Marlo, believing that Joe's time has come, and that Marlo's tenacity and ambition will not allow him to accept the Greeks' rejection of his business overtures.
After Marlo has Proposition Joe murdered, he received the blessing of Vondas to be Joe's replacement as agent between Vondas' drug shipments and the New Day Co-op's drug distribution activities.
Later, Stanfield's first re-supply with the Greeks is busted by the Major Crimes Unit, and as part of a deal with the State's Attorney's office, Stanfield is forced to retire from his life of crime. To set himself up for life, Stanfield sells the connection to the Greeks to whoever can pay him ten million dollars. In the series finale, Vondas is seen meeting with Fat Face Rick and Slim Charles at Little Johnny's Diner. They are discussing the new business arrangement while The Greek quietly listens in the background.