Nantz led a team of security contractor in ambushing Jack Bauer's medical convoy with orders from Charles Logan. He was taken back to a parking lot under the Williamsburg Bridge to be executed. As Nantz took Jack to a position to shoot him, he told Commando 1 to prepare the other men, and that they would rendezvous with Team B in twenty minutes. As the other commando left, Nantz told Jack that he knew who he was. Out of respect, he would make Jack's death fast. Jack tried to escape by taking out Nantz' legs, but Nantz overpowered him and punched him several times in the face while telling Commando 1 to stand down.
Once he had Jack back in his position, he prepared to shoot him. Just before he could, Commando 1 stopped him. He had PresidentAllison Taylor on the line. Nantz spoke to Taylor, who told him that she had a UAV drone tracking their position. She warned Nantz that if they did not release Jack Bauer and leave, she would have the drone fire its missiles at them. At first confused, Nantz agreed and called for his team to go. He then, upon Taylor's orders, gave the phone to Jack, and evacuated the scene. ("Day 8: 3:00pm-4:00pm")
Although Nantz remained unnamed during the episode, his name was given in the FOX.com episode recap.
Dialogue given by Nantz suggested that it was quite a large operation. He said that they would meet with another team in twenty minutes, but the other team's task was never revealed. It is highly likely that Nantz's group worked for the same contractor which employed Mark Bledsoe and others (including Haigney, Mullins, etc.) who were Logan's mercenaries active just a few hours earlier.