TB4 appears in eight episodes, piloted at all times by IR aquanaut Gordon Tracy.
In the compilation episode Security Hazard, TB4 is seen only in flashback footage (from Day Of Disaster). The mini-sub makes brief cameo appearances in both of the feature films (Thunderbirds Are Go (film) and Thunderbird 6).
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 TV reporter 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 Navy carrier U.S.N. Sentinel. International Rescue contacted the very same strike vessel, requesting 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 - not only was the rocket itself too heavy, but a large storm had 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. After the stubborn bridge controller refuses to call International Rescue, Brains furtively makes the call himself from the control tower, telling John up in Thunderbird 5 what they'll need for the rescue itself.
Thunderbird 2 soon arrives and drops Pod 4 into the river, releasing Thunderbird 4. With the rocket covered in debris from the bridge, Gordon uses the laser cutter within TB4's nosecone to cut through it, whilst TB2 lifts the debris from the riverbed and dumps it on land. The process proves to be too time-consuming, and Brains advises Gordon to sharp-shoot the debris using TB4's torpedo launcher. He's firmly convinced that the explosion wouldn't damage the rocket itself; and, as usual, he's correct. TB4 is then able to use its battering rams to knock off the nosecone containing the two astronauts, thus freeing them in time from the rocket - which then blasts up from the river, and subsequently explodes in the sky.
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 - again - by The Hood. The following morning, after Tin-Tin has told the Tracy brothers, TB2 deploys Thunderbird 4 into the lake, to find Brains before the air in his diving-tanks expires...
During the search, though, The Hood - using torpedoes from his own submarine - attacks TB4. The yellow mini-sub survives and returns fire, damaging The Hood's aquatic vessel, which subsequently blows up just after he manages to escape. Gordon then resumes his search for Brains and, with Scott's assistance, successfully rescues him.
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 TB4's laser cutter to cut off Fireflash's engines, causing the massive plane to float to the surface of the sea.
After surfacing, Fireflash's control panel suddenly bursts into flames, again putting the lives of the crew in danger as they start to suffocate in smoke. Gordon then surfaces alongside them in TB4, and - with TB2 standing by overhead - he climbs onto the plane with a reinforced glass-cutter to break into the cockpit. The crew is able to escape aboard TB2, as Fireflash explodes and sinks soon after.
The Mighty AtomEdit
Bombs planted by The Hood explode all around 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 station's sea intake, as Gordon 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 from her yacht FAB 2, off the French Riviera, and traps her on a boat in a deserted boathouse - along with a bomb that is set to explode. She's able to persuade him to let her "freshen up" before being tied up, thus allowing her to secretly contact Jeff Tracy. She's 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, carrying Pod 4.
As Thunderbird 4 quietly submerges, Scott utilizes Thunderbird 1's Sonar Tracking System to find the mastermind Carl. Gordon is then able to pinpoint the precise location of the red submarine in which Carl and his cohorts-in-crime are hiding. He uses TB4's paralyzer to drill into the crooks' sub and neutralize them with knock-out gas, before Carl can set off the bomb elsewhere - allowing Scott to subsequently rescue Penelope.
Attack of the Alligators!Edit
In a secluded laboratory located along the swampy Ambro River, giant alligators are created due to the accidental release of a growth drug produced in the lab, called Theramine. International Rescue are called to save the locals from the gators, but a boatman Culp, who wishes to steal the drug, escapes in a boat with the last batch of it in a phial - which ends up at the bottom of the river when the boat is attacked and destroyed by the gators. Thunderbird 4 is deployed into the murky river-depths to find the phial - if it hasn't smashed.
Gordon leaves TB4 and takes to the river - where it doesn't take long for him to find the phial, which thankfully still contains all the Theramine and hasn't sustained any damage.
The story of Day Of Disaster is briefly retold in a flashback sequence, using footage from the episode.
Thunderbird 4's final appearance in the series, and its only appearance in Series 2.
The W.N.S. Reaper, an atomic submarine with nuclear weapons, is being tested by the Navy. One of two missiles launched by the sub 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 and their crew are working. International Rescue are called, and as Thunderbird 2 prepares to launch with Pod 4, TB4 is hooked up to a sealing device, which will be needed to block the escaping gas and extinguish the fire.
Upon TB2's arrival, Pod 4 is dropped near the oil rig and TB4 descends to the fire, towing the sealing device behind it. The blaze dies out once the sealing device securely clamps down on top of it; and all appears to be well. Unfortunately, hours later, the seabed starts to become unstable once again, resulting in more violent explosions, these much nearer to Seascape than before. International Rescue decides to leave the rescue of the rig's crew to the Navy, who plan to airlift everyone off within two hours. But then, a large wave damages one of the huge rig's supporting legs; and Frank and Dick decide to investigate in a diving sphere. Suddenly, another column of flame explodes, severing the diving sphere's cable and sending it - with Frank and Dick still inside - to the seabed, where only International Rescue can reach them in time. Thunderbird 4 returns, and uses electromagnets within its Battering Rams to lift the diving sphere to the safety of the surface.