Warriors of the Deep is the first serial of the 21st season of the British science fiction television series Doctor Who, which was broadcast in four twice-weekly parts on BBC1 from 5 to 13 January 1984.
In the serial, two human power blocs, along with members of the Silurians and Sea Devils, the original rulers of the Earth, battle for control over the nuclear missiles on an undersea military colony on Earth in 2084.
Plot
In 2084, Earth is divided into two opposing superpower blocs. A bloc has created a secret underwater base, Sea Base 4, which has nuclear weapons aimed at the opposing bloc. The base's crew is led by Commander Vorshak and his senior officers, Nilson, Bulic and Security Chief Preston. Vorshak and Bulic noticed something strange on their long range sensors, but dismiss it as a trivial glitch. In reality, the glitch is a Silurian battlecruiser led by Icthar, the sole survivor of the Silurian Triad and his subordinates, Tarpok and Scibus, who are monitoring Sea Base 4.
Inside the TARDIS, Turlough has changed his mind about going home, and the Fifth Doctor plans to show Tegan something of Earth's future. As the TARDIS materialises in space, it is attacked by Sentinel Six, a robot weapons system. The Doctor saves the TARDIS by materialising on Sea Base 4.
Sea Base 4 undergoes a practice missile run, but Maddox, the temporary sync operator, faints afterwards. Vorshak realises that the function of the base will continue to be compromised due to Maddox. Nilson and the Base's chief medical officer, Doctor Solow, who are enemy agents for the opposing bloc, plan to program Maddox to destroy the computer circuitry. They reprogram Maddox in the Base's psycho-surgery unit.
Turlough summons a lift, alerting the crew of his and the Doctor's presence - they are captured by Preston.
The Silurians revive the Sea Devil warriors and their commander, Sauvix. The Silurians and Sea Devils launch an attack on the base and the Doctor tries to warn Vorshak not to fire on them. Vorshak ignores him, and, as a result, the Base's defences are neutralised by the Silurians' deflection beam. The Silurians then dispatch the Myrka, a large marine monster. During the attacks, Solow and Nilson activate Maddox, who tampers with the equipment. When Ensign Karina becomes suspicious, Nilson makes Maddox kill her. The Myrka makes its way towards the bridge, killing several people, including Doctor Solow, but the Doctor eventually destroys the Myrka by using an ultraviolet light generator.
The Silurians prime a device called the manipulator and prepare to arrive on the base. The Sea Devils break in and start the push for the bridge. Nilson kills Maddox and attempts to escape by taking Tegan hostage but the Doctor blinds him with the ultraviolet device. A group of Sea Devils arrive and kill Nilson, while Tegan and the Doctor are taken as prisoners to the captured bridge.
The Doctor recognises Icthar and confronts him about the massacre. Icthar intends to get mankind to destroy itself by triggering a global war. The Doctor escapes from the bridge and discovers some cylinders of hexachromite gas, which is lethal to all reptile life. Preston urges the Doctor to use the gas on all of the Silurians and Sea Devils, but the Doctor adamantly refuses. The Doctor changes his mind when Turlough reminds him of what the Silurians intend to do if they launch the missiles. When he is unable to find anything else less lethal, he begins to connect the gas containers to a central air pump. The Doctor is discovered by Sauvix before he can turn the pump on, Preston is killed by Sauvix, who is sprayed with gas and killed by Bulic. As the Silurians prepare to fire the missiles, the Doctor feeds the gas into the ventilation system. Bulic stays in the chemical store to ensure that the gas keeps flowing, while the Doctor and his companions leave for the bridge to try to stop the Silurians.
The warriors begin to collapse from the gas and the Doctor tells Tegan and Turlough to give the Silurians oxygen to keep them alive. The Doctor, aided by Vorshak, tries to stop the missiles by linking himself into the equipment as the sync operator. The Doctor succeeds, but Vorshak is killed by Icthar, who himself is killed by Turlough, leaving the Doctor, his companions and Bulic the only survivors. Left in despair, the Doctor laments the deaths.