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The Sea Devils

The Sea Devils was the third story in the ninth season of Doctor Who. It marked the first appearance of the Sea Devils and the reappearance of the Master, now plotting to escape confinement from a maximum security prison.

Barry Letts and Terrance Dicks had decided they wanted a sea-based story and asked Malcolm Hulke to write it. Rather than merely bringing back the Silurians, Hulke invented an aquatic version called the Sea Silurians. Unlike their earlier counterparts, these “Sea Devils” were given clothing, designed by Maggie Fletcher.

To answer the insistence by fans that the Silurian era of 200 million years ago could not have spawned the Apes who featured in the earlier serial, Hulke introduced a line in which the Doctor says they should correctly be called Eocenes. However even that period, some 50 million years ago, was still somewhat in advance of the evolution of primates.

After the Master appeared in all five stories of season 8, Letts decided to restrict him to a few appearances each year. This story joins him where The Dæmons left off, in prison. The dialogue implies the Doctor and he were once friends.

Letts had secured the involvement of the Royal Air Force for The Mind of Evil and decided to try to do the same with the Royal Navy. He found the Ministry of Defense eager to take part. Shortly after broadcast, the BBC was visited by officials from the MOD who believed a top-secret submarine had been used in the show. It was in fact a model, adapted to show the features they were secretly testing.

Expensive location filming left The Sea Devils with a budgeting problem. Director Michael Briant’s solution was to not hire regular incidental music composer, Dudley Simpson, and have the score created by the BBC Radiophonic Workshop. Malcolm Clarke’s electronic score was one of the serial’s signatures.[1] Its significance was attested to by its inclusion in2013’s Doctor Who at the Proms, where it was one of five pieces of incidental music performed as representative of the show’s original run.

This story saw the only use of the catchphrase “reverse the polarity of the neutron flow” during the Pertwee era. The phrase became associated with the Third Doctor, so he used it again in The Five Doctors some eleven years later, although between seasons 7 and 11 Pertwee did use a shortened version of the phrase, “reverse the polarity”, several times.

Like many of Hulke’s stories, it included a moral dimension. The Sea Devils are caught between the Master, the Doctor and the humans. Ultimately, they are betrayed by all three; like their land-based cousins, it is the humans who hurt them the most.


Episode 1

The Doctor and Jo visit the Master, now a captive on a small island prison after being captured by UNIT.

The Master is being held indefinitely and is the only prisoner. He is watched by CCTV and the island is patrolled by armed guards – trained to resist the Master’s hypnotic powers – and even protected by minefields. He claims to have reformed – but refuses to reveal the location of his TARDIS. As they depart, the old-school, patriotic governor, Colonel Trenchard, tells them that some ships have been disappearing mysteriously. Shortly afterwards, he visits the Master, and it becomes clear that they are in league.

The Doctor cannot resist investigating, so they visit the nearby naval base, HMS Seaspite, run by the efficient Captain John Hart; despite the Doctor’s eccentric behavior – he claims to have known Nelson personally – an alliance forms. The Doctor states that that the linear scorch pattern was caused by a concentrated beam of heat from under the sea. Hart is in charge of the adaptation of the sea fort to a SONAR testing station. The Doctor and Jo make their way to the sea fort. He and Jo are soon attacked by a Silurian lookalike.

Episode 2

It is not a Sea Devil, but a half-mad crew member ranting about them. The Doctor and Jo decided to calm him down. They find that the radio was ripped out. The Doctor decides to go get a transistor radio in order to turn it into a transmitter. On his way, he encounters a hostile Sea Devil, who fires at him. When it tries to break in, it is hurt and flees. Shortly afterwards, the Doctor finishes his transmitter, and they are rescued.

Captain Hart decides to find them after they apparently disappear. The Doctor and Jo attempt to get Hart to tell a higher authority. His assistant gets a call from someone ranting about Sea Devils. The Master comes to HMS Seaspite to steal some equipment. Colonel Trenchard follows, providing a distraction, but Jo sees the Master leaving.

The Doctor and Jo confront Trenchard, and he tries to dissuade them by showing that the Master is in his cell. The Master knocks out a guard and grabs his knife. Trenchard then gets the Doctor to go and see the Master, who attempts to kill him, first with gun and then with sword. The Doctor and the Master engage in a sword fight. The Master then throws a dagger at the back of the Doctor’s head….

Episode 3

The Master misses and the Doctor is unharmed. Trenchard decides to lock the Doctor in the prison and attempts to capture Jo. The evil Time Lord tells him that he intends to use the reptiles as an army to conquer the planet. It is revealed that the reason Trenchard is helping the Master because he believes they are fighting enemy agents. Meanwhile, Jo comes and frees the Doctor. He begins by using the machine to summon Sea Devils from the ocean. The Doctor and Jo are trapped between them, the Master, and the minefield!

Episode 4

The Doctor is forced to employ his sonic screwdriver to repel the Sea Devils by exploding mines on the beach. While the Doctor and Jo navigate through a mine field, a Sea Devil attacks another submarine. The Doctor and Jo flee to HMS Seaspite, where Hart tells them another naval submarine has disappeared.

Meanwhile, the Master returns to his cell to begin work on a new device. He activates it and it calls the Sea Devils to him. They attack the prison, killing the guards and Trenchard. A battle for the prison rages. Trenchard, who believed he was aiding his country against enemy agents, is killed.

HMS Seaspite heads out to investigate a section of seabed. The Doctor goes down in a diving bell. When they offer to pull him up, he refuses; however, his communication system fails, and Captain Hart orders the crew to pull up the diving bell. When it reaches the ship, it is empty….

Episode 5

The Sea Devils take the Doctor to their leader. The Doctor enters the Sea Devils’ base and tries to encourage peaceful negotiation, recalling how he had failed to broker an agreement between mankind and the Silurians. The Master arrives to incite matters by trying to provoke war.

Walker arrives to “solve” the sinking ship problem by dropping depth charges. Meanwhile, the Doctor has gained the upper side of the argument–the Sea Devils agree to consider diplomatic relations. The depth charges disrupt the negotiations. The Master convinces the Sea Devils to take the Doctor away and kill him. He also convinces them to attack one of the naval bases.

In the confusion caused by the depth charges, the Doctor escapes, gets a Silurian gun from a fallen Sea Devil, and uses it to melt a door and rescue two of the submarine crew. They rescue the others still in the submarine. The leader of the submarine crew kills one of the Sea Devils with the gun that the Doctor picked up; it is implied that others were killed on the upper level of the sub. They try to leave, but the Sea Devils hold them back with a force field. They fire torpedoes to provide thrust and escape.

The Doctor confronts Walker about his depth charges, which have just made the Sea Devils angry. The Sea Devils rise and attack the HMS Seaspite. As the Doctor attempts to go down to negotiate again, a Sea Devil raises its gun at them….

Episode 6

The Doctor fights the Sea Devil off with Venusian karate, but another captures him. The rest of the Sea Devils capture the rest of the people at the base. Jo, Captain Hart, and Mr. Walker are held in one of the offices at the base. The Master tells the Doctor that he needs help to complete his machine so he can revive the colonies all over the world.

Meanwhile, Jo and escapes through a ventilation shaft. Jo reaches the Doctor and he tells her that he will deal with the guards; he sends her back to retrieve Captain Hart and Mr. Walker. The Doctor makes the machine emit a shrill noise which puts the Sea Devils in agony. Captain Hart escapes with Jo, but Mr. Walker retreats into the office and shuts himself back in when faced with a Sea Devil, even though the creature is incapacitated by the noise from the machine. The Master shuts off the machine, and the Doctor apologizes for the “mistake” that caused the noise. The Sea Devils, the Doctor, and the Master head back to the Sea Devil base.

The prisoners retake the base. A soldier arrives and the Doctor orders him to keep watch over the Master, but the Master hypnotizes him and escapes. The Doctor chases after the Master, and they reach the base, where multiple Sea Devils capture them. Meanwhile, Walter orders a nuclear strike. The Doctor sabotages the machine, and the Time Lords are imprisoned. The Doctor reveals that he reversed the polarity of neutron flow, which will cause a massive explosion. The Time Lords escape by using the Doctor’s sonic screwdriver to get out of their cell; they find diving suits and exit the base. They rise to the surface and are rescued just before the base explodes, and the Sea Devils are destroyed.

The rescuers call an ambulance for the Master, who seems to be very ill; however, when the ambulance arrives, they realize that the man is not really the master, but someone else wearing a disguise–the Master has hypnotized him and forced him to impersonate the Master. They realize that the Master is escaping in a hovercraft.


The Third Doctor
Jo Grant