In an oil field, a fire rages at one of the wells. Virgil drives the Firefly in, shooting an explosive charge to successfully blow out the fire. An NTBS news crew is watching as the Firefly returns to Thunderbird 2. They're angry that International Rescue prohibits photography of their top secret equipment. Reporter Ned Cook decides to flout the rules anyway, ordering his cameraman, Joe, to shoot as Thunderbird 1 takes off. But the Automatic Camera Detector goes off, alerting Scott to their actions. He lands next to the news truck and demands they destroy the tape. Ned refuses and floors the gas pedal. Scott takes off again, chasing Ned down the road. Scott electromagnetically wipes the videotape then leaves. Jeff is dictating a letter to Tin Tin when he receives word from Virgil that the mission was successful. He returns to dictating the letter praising the moving of the Empire State Building and the redevelopment of the area. Virgil sees a radar contact from the water and notifies Scott. Based on its 200 knot speed, they conclude it's the Sentinel, the navy's newest strike vessel. On board the Sentinel, the captain hears about radar tracking an aircraft moving at 5000mph. With no official aircraft scheduled in the area, they conclude it's not an aircraft. Virgil changes course to avoid giving the Sentinel any clues to the location of their headquarters. But that places him on course to New York City. The Sentinel receives orders to destroy the radar contact. They fire two missiles at Thunderbird 2. Virgil uses a radar jammer, which forces near misses. The Sentinel fires two more on a different frequency. Virgil climbs at the last moment, but Thunderbird 2 is hit. With systems damaged, Thunderbird 2 plunges toward the sea. Jeff calls Washington, which orders the Sentinel to cease its attack. The Sentinel explodes its fifth and sixth missiles. Virgil regains consciousness just in time to pull Thunderbird 2 out of its dive. At the island, they make plans to receive the damaged aircraft, with gooseneck nozzles coming out of the ground to cover the runway. When Thunderbird 2 lands, its wheels collapse as it skids to a halt. The nozzles release foam to quell the fire. Virgil awakes to find Jeff and Scott standing over his bed. They tell him Thunderbird will be repaired in a few weeks. After Virgil finishes a meal, Gordon enters his room to tell him to watch the Empire State Building being moved on TV. Virgil excitedly turns on his TV as the rest of the family gathers in the living room to watch. Ned Cook reports from the scene, explaining how the building was jacked up then underlaid with heavy-duty track. An atomic-powered engine will move the building along the track. Ned's enthusiasm when the engine starts moving changes to concern moments later when the ground begins cracking beneath the tracks. The engine is stopped and Ned is ordered to leave the scene, but a pit opens beneath Ned and Joe before they can move. The building topples soon afterward, covering up the pit as it's reduced to rubble. The camera is destroyed in the fall, but Ned and Joe continue to broadcast audio. Ned says that Joe is "in a bad way" and they can hear water coming into the pit. Brains surmises that the collapse was because of an undetected underground river undermining the tracks. Gordon wants to take Thunderbird 4 to the scene, but it's only a short-range craft. Jeff is angry at the Sentinel for damaging Thunderbird 2, which gives Virgil the idea to use the Sentinel to transport Thunderbird 4. Jeff orders Thunderbird 1 on scene while he contacts Washington for the Sentinel's help. Thunderbird 4 launches via an emergency ramp and is later hoisted onboard the Sentinel, but it will take them 24 hours to get to New York. Thunderbird 1 arrives in New York, where Jeff orders Scott to pass breathing apparatus down to the trapped men to keep them alive until Thunderbird 4 arrives. In the pit, the men shiver in the cold water rising up to their waists. As they get the breathing gear, the water rises faster, cutting their safety margin. The Sentinel can't go any faster. The men don the gear as planned. The Sentinel approaches New York but must slow down to avoid the shipping traffic in the harbor. Gordon suggests releasing Thunderbird 4 so he can move faster beneath the shipping. With little air remaining, Scott tells the men to search for their end of the underground river. Scott receives bad news. A neighboring structure, the Fulmer Finance Building, is in danger of collapse, which can crush the area they're in. The men are almost out of air when they see the opening of the underground river and swim for it. Thunderbird 4 navigates the winding passage when they finally see its lights. The men get inside just before the Fulmer building falls. Thunderbird 4 is buffeted, but otherwise safe. Ned Cook returns to host his show, which he has not missed in 167 weeks. He comes onstage in a motorized wheelchair and gives International Rescue his heartfelt thanks. Unbeknownst to Ned, watching from the back row are the Tracy family and their friends and servants.