Thunderbird 4 appears in nine episodes, but only as a flashback to a previous episode in one of them, namely Security Hazard. Thus, it is used in eight rescue missions total, piloted at all times by Gordon Tracy.
Terror in New York CityEdit
Thunderbird 4's debut, and first rescue mission. When the Empire State Building in New York collapsed after an attempt to move it two hundred yards, it left Ned Cook and his cameraman Joe trapped in an underground river, with the water slowly rising.
It was made clear that the submarine is merely a scout craft, and would have to be transported to the danger zone via Thunderbird 2. Earlier in the episode, however, Thunderbird 2 was shot down by the U.S.N. Sentinel. International Rescue contacted the very same strike vessel, and requested that they transport Thunderbird 4 to New York City. They accepted the request, and Thunderbird 4 was deployed from Tracy Island to the U.S.N. Sentinel, which then headed to the coast of New York. The trip took an entire day, but with Thunderbird 1 already there the whole time and Scott Tracy providing Ned and Joe with supplies and encouragement, there was still time.
Thunderbird 4 traveled through the cramped underground river, and Gordon eventually found Ned and Joe barely conscious. They were both able to swim into the hatch, and Thunderbird 4 was able to escape the river before another nearby building could collapse on top of them.
Day of DisasterEdit
In England, the Allington Suspension Bridge collapses whilst the Martian Space Probe is carried across it, for not only was the rocket too heavy, but a large storm damaged the bridge the night before. The impact of the rocket hitting the sea bed, in an upright position amazingly, activates the countdown, threatening the lives of the two people inside. Brains, who visited the bridge shortly after the incident, calls International Rescue after the stubborn bridge controller refuses to do so.
Thunderbird 2 soon arrives and drops Pod 4 into the water, releasing Thunderbird 4. With the rocket covered in debris from the bridge, Gordon uses the laser cutter within Thunderbird 4's nosecone to cut through it, whilst Thunderbird 2 lifts up the debris and dumps it on land. The process proved to be too time consuming, and Gordon was advised by Brains to shoot the debris with Thunderbird 4's torpedo launcher, firmly convinced that the explosion wouldn't damage the rocket itself. Brains was right, as usual, and Thunderbird 4 was able to use its battering rams to knock off the nosecone containing the two astronauts, thus freeing them from the rocket before it could explode and kill them horribly.
Brains and Tin-Tin are on a treasure hunting expedition at North Africa's Lake Anasta, with no idea that The Hood is spying on them and planning to steal whatever interesting things they find. After one attack by The Hood, resulting in Brains wearing a sand necktie, Scott and Virgil show up in Thunderbirds 1 and 2 to ensure their safety. They all camp the following night, but Brains wakes up and tells Tin-Tin he's going back into the lake, leading to him being knocked out by The Hood's powers. The following morning, after Tin-Tin has told the Tracy brothers, Thunderbird 2 deploys Thunderbird 4 into the lake in search of Brains.
During the search, The Hood attacks Thunderbird 4 with torpedoes using his own submarine, but Thunderbird 4 remains functional. Gordon fires a torpedo back, and blows up The Hood's aquatic vessel before resuming the search for Brains, which ends up being successful.
After Fireflash 4 mysteriously crashes into the ocean and sinks to the seabed, Thunderbird 4 is taken to the scene to save the crew. Gordon briefly swims out of the yellow submarine to inform the crew of his rescue plan via the Light-Type. He then uses Thunderbird 4's laser cutter to cut off Fireflash's engines, causing the plane to float to the surface of the sea.
After floating all the way, the control panel on Fireflash suddenly bursts into flames, putting the lives of the crew in danger as they start to suffocate in smoke. Gordon then rises to the surface with them in Thunderbird 4, and climbs onto the plane with a reinforced glass cutter to break into the cockpit. The crew is able to escape, with Fireflash exploding soon after.
The Mighty AtomEdit
Bombs planted by The Hood explode all over the Atomic Station in the Sahara Desert, causing a large fire that threatens to destroy the entire station and create a deadly radioactive cloud. Thunderbird 2 delivers Thunderbird 4 to the stations sea intake, as he must destroy it with torpedoes at a very precise moment to stop the station from exploding. Scott and Virgil enter the control cabin, and attempt to bring the station under control using the rods, immediately after which, Gordon opens fire. His timing was bang on, and the station was saved.
The Man From MI.5Edit
Carl kidnaps Lady Penelope and traps her on a boat in a deserted boathouse that is set to explode. She is able to persuade him to let her "freshen up" before being tied up, thus allowing her to secretly contact Jeff Tracy. She is unable to tell him much about her situation, but with the location clued in, Scott and Virgil are sent to the scene in Thunderbird 1 and Thunderbird 2, the latter of course carrying Pod 4.
While Virgil saves Lady Penelope, Scott and Gordon focus on tracking Carl. Using Thunderbird 1's Sonar Tracking System, they discover that Carl and his men are hiding in a submarine at the bottom of the water. Gordon use's Thunderbird 4's paralyzer to drill into the submarine and knock out the criminals with knock out gas.
Attack of the Alligators!Edit
In a laboratory located at a swamp, giant alligators are created due to the accidental release of growth drug produced in the lab called Theramine. International Rescue are called to stop the alligators, but a boatman Culp, who wishes to steal the drug, escapes in a boat with the last batch of it in a phial. This ends up at the bottom of the swamp when the boat is attacked by the alligators. Thunderbird 4 is deployed into the murky swamp to save the phial, if it hasn't smashed.
It doesn't take long for Gordon to find the phial, which thankfully still contains all the Theramine and hasn't sustained any damage.
A flashback episode, where the story of Day of Disaster if briefly retold using old footage.
Thunderbird 4's final appearance in the show, and only appearance in Series 2.
The W.N.S. Reaper, an atomic submarine with nuclear weapons, is being tested by The Navy. One of the two missiles launched by the submarine goes off course and explodes on the seabed, causing an underwater oil pipe to explode and burn, threatening the nearby Seascape drilling rig, where Frank Hooper and Dick O'Shea are working among other people. International Rescue are called, and as Thunderbird 2 prepares to launch with Pod 4, Thunderbird 4 is hooked up to a sealing device, which is needed to block the escaping gas and extinguish the fire therefore.
Upon the arrival of Thunderbird 2, the pod is dropped nearby the oil rig, and Thunderbird 4 descends to the fire and clamps down the sealing device on top of it, stopping the burning. Unfortunately, hours after leaving, the seabed starts to become unstable once again, resulting in more violent explosions nearby the oil rig. International Rescue decide to leave rescue of the crew to the Navy, who plan to airlift them out within two hours. While waiting, a large wave damages one of the rig's legs, and Frank and Dick decide to investigate it within a diving sphere. Suddenly, another column of flame explodes, and cuts the diving sphere's cable and sends Frank and Dick to the seabed, where the Navy is unable to go. Thunderbird 4 returns once again, and uses the electromagnets within its Battering Rams to lift the diving sphere to the surface and save the two men.