Here are some rough notes that I made about another archetypal Doctor Who plot structure:
Alien Invasion!The classic Doctor Who invasion stories are inextricably linked to the Pertwee era, although the basic formula was developed during the latter half of the Troughton era. Some of the most iconic moments in the history series come from these stories.
Alien invasion stories can be effective, but they should be used sparingly -- you want to avoid the “invasion of the week” syndrome if possible. In addition, running too many alien invasion stories back-to-back stretches the credulity of the audience (i.e. the players). Personally, I recommend that you shouldn't do more than a single story of this type each season.
It is interesting to note that invasion stories in Doctor Who tend to have a unique structure that is slightly different to the B-Grade alien invasion films of the 1950s. Many of the differences are due to the episodic nature of the TV series and the need to string out the invasion story over four to six episodes.
Classic Doctor Who invasion stories are usually built around an iconic moment when the nature of the alien threat is openly revealed - the Cybermen emerge from the sewers, Auton dummies smash through shop windows, etc. These moments typically occur quite late in the story. In a four-part story, they tend to occur towards the end of episode three and in a six-part story they tend to occur late in episode four or early in episode five. The reason for this is pacing - once the alien menace is openly revealed, the story needs to move briskly towards the climax.
In many cases, the presence of the aliens is not revealed to the Doctor until the climax of episode two. Typically, the Doctor is confronted with a mystery in episode one that leads him to gradually uncover evidence of alien activity.
One common feature of Doctor Who invasion stories is the presence of a human collaborator who gains access to alien technology in exchange for assisting the invaders with their plans. The archetype of the human collaborator appears again and again in Doctor Who, from Tobias Vaughn in
The Invasion through to Luke Rattigan in
The Sontaran Strategem.
In most cases, the human collaborator is a wealthy entrepreneur who is uses advanced alien technology to develop and market revolutionary devices that are far beyond their time. Examples include the electronic circuitry developed by International Electromatics, the ATMOS devices in the
Sontaran Stratagem, and the advanced plastics in
Terror of the Autons.
The new technology introduced by the human collaborator typically has four major features.
- The new technology has become ubiquitous very quickly, grabbing market share from competing products in a matter of months.
- The new technology is more advanced than should be possible with contemporary human technology.
- The new technology has a sinister purpose that is not immediately evident. Often a character who examines an example of the device early in the story will find evidence of parts that are not obviously related to its supposed purpose.
- It should embody contemporary concerns about technology in some way. For example, the electronic devices produced by International Electromatics in The Invasion reflect concern about the spread of consumer electronics in the late 1960s. The plastic toys in Terror of the Autons reflect concerns about the spread of plastics and automation in the 1970s. And the ATMOS devices in The Sontaran Strategem reflect 21st century concerns about atmospheric pollution and global warming.
The motivations of the human collaborator are important. Often, the human collaborator has a change of heart late in the story and allies himself with the Doctor once he realises that his alien allies plan to betray him. For example, Tobias Vaughn tries to use the Cerebration Mentor against the Cybermen, George Hibbert tries to destroy the Auton machinery at Auto Plastics, Luke Rattigan uses his Atmospheric Converter to blow up the Sontaran ship, and so forth.
Typically the collaborator is killed by his former alien allies as he redeems himself with a heroic act that destroys the invasion force....or at least slows it down for long enough for the Doctor to implement the measures necessary to defeat it.
Early in the story, the Doctor begins to suspect that the human collaborator is in contact with an alien intelligence of some kind and confronts the collaborator verbally. Subsequently, the collaborator either decides to eliminate the Doctor as a potential threat or is ordered by his alien allies to do so.
Previously, the audience may have witnessed the collaborator kill a journalist, private investigator, or UNIT agent who has gotten too close to the truth, demonstrating that this is no empty threat. An attempt to eliminate the Doctor by conventional means often forms the climax of the first episode.
Although the Doctor survives the initial attempt to eliminate him, the actions of the villain confirms his suspicions that something is seriously wrong. Typically, he decides to sneak into a factory or industrial facility owned by the human collaborator in order to discover the true nature of the threat. Depending upon the story, the Doctor may need to dodge security guards and cameras to research the location where the secrets are held. Typically, the Doctor discover some incriminating evidence that reveals the true magnitude of the threat. Often he will encounter one or more inert members of the alien invasion force - cybermen cocooned in packing crates, inert autons, etc. This discovery often forms the climax of the second episode.
At the beginning of the third episode, the aliens realise that the human authorities are close to discovering the truth and decide to bring their invasion plans forward.
The third episode in the story often adventure features the use of alien simulacra to infiltrate the command structure of the human authorities. For example, in
Terror of the Autons, the invaders used duplicates of miliary leaders and politicians. And in
The Sontaran Strategem, the invaders used clones to infiltrate UNIT - even going so far as to produce a clone of the Doctor's companion!
The third episode usually ends with the moment when the alien invasion is openly revealed. This is the iconic moment that people tend to remember - Cybermen on the steps of St. Paul's cathedral, Autons coming to life in shop windows, etc. It is worth putting a bit of time and effort into the moment where the alien menace is revealed - try to come up with a strong visual image that communicates the immediacy of the threat to the players.
Immediately after the aliens emerge into the open and begin to execute their plans, there is a set-piece battle that underscores how helpless the humans are in the face of the menace. This is the scene where dozens of UNIT soldiers blaze away ineffectually against the advancing aliens. It is interesting to note that the new series contains an excellent example of this trope in
The Sontaran Stratagem.
At the beginning of the fourth episode, the Doctor usually develops a device that can weaken but not destroy the alien invaders, giving the human forces a chance to hold them at bay for long enough for him to develop a more permanent solution.
Shortly afterwards, the human collaborator realizes that he has been duped by his alien allies and he has a change of heart. In many cases he attempts to use their own technology against them. This act of defiance is futile, but buys the Doctor some additional time.
Finally, the Doctor develops an ingenious solution to the alien menace that allows him to deactivate or disable most of the minions of the alien leader. The Doctor must then confront the leader of the alien invasion force before he has a chance to call in overwhelming reinforcements. At the climax of the story, the alien leader is killed and the approaching reinforcements are destroyed.
