The Edge of Destruction ( TV story ) The Edge of Destruction was the third story of Season 1 of " Doctor Who " . The story is unique in the original series in that it is set entirely inside the TARDIS and features only the regular cast members . The BBC initially committed to four episodes of " Doctor Who " . Mid - way through the production of " An Unearthly Child " , this was upped to thirteen . Together , " An Unearthly Child " and " The Daleks " only totaled eleven . With a tiny budget , " The Edge of Destruction " was commissioned to fill the remaining two episodes and fill out the season . Narratively , the story was crucial as its events bonded the travellers so they were no longer just mismatched people forced together but a group who could trust one another . It also offered the first hint that the Doctor ' s TARDIS was not his own , shown by his lack of understanding of its abilities . Finally , it was also the first instance of the Doctor namedropping historical figures . The second episode of this serial , " The Brink of Disaster " , is as far as viewers can watch the Hartnell era , and the series itself from the very beginning in televised format , before running into a single missing episode : the following serial , " Marco Polo " , remains absent in its entirety . Synopsis . As they slowly recover from the shock of being thrown to the TARDIS floor , the Doctor , Susan , Ian and Barbara all seem to be acting strangely . Unexplained events occur and suspicions are raised that an alien force may have entered the ship . The Doctor even accuses Ian and Barbara of sabotage . It gradually dawns on the travellers that what they have been experiencing is an attempt by the TARDIS itself to warn them of something . The Doctor finally realises the fast return switch he used when leaving Skaro has stuck , and the ship has been plunging back to the beginning of time and its own destruction . Once the problem — a faulty spring — is corrected , the TARDIS returns to normal and the Doctor has to make some apologies for his behaviour . Plot . The Edge of Destruction ( 1 ) . The Doctor , while attempting to correct the TARDIS ' faulty navigation circuits , causes a small explosion . The Doctor , Barbara , Ian and Susan are all rendered unconscious . Barbara is the first to recover and awakens Ian and Susan , who appear to have slight cases of amnesia . The Doctor lies on the floor with a gash on his head . Susan recovers her senses enough to retrieve a special healing bandage from the ship ' s first aid kit and water from the food machine for her injured grandfather . Suddenly , Susan becomes convinced that an alien presence is on board and has seized control of the ship . The TARDIS doors begin erratically opening and closing whenever Ian moves towards them . When Susan tries to operate the door switch on the console , she receives an electrical shock . As the Doctor revives , Barbara tends to him while Ian carries Susan to her room . There she stabs at him with a pair of scissors , rips her bed to shreds , then collapses . Later , the Doctor , Barbara , and Ian discuss the situation , each alternating between clarity of mind and paranoid sniping . The Doctor checks the system controls with Ian ' s assistance , while Barbara checks on Susan . Susan has retrieved the scissors and tries to attack Barbara , but stops herself from doing any real harm . When the Doctor tries to determine their location with the view scanner , he finds only images which he recognises as records of the TARDIS ' earlier trips . The last image , a picture of planets , a solar system and an explosion , puzzles him . By now , Susan is convinced that not only has an alien intelligence entered the ship , it has taken over at least one of the people . When the Doctor opens the TARDIS doors , they quickly close themselves when Ian approaches them . Soon , the Doctor and Susan begin to accuse their human companion s of sabotage to get the TARDIS back to England in 1963 . Barbara angrily refutes the Doctor ' s suspicions with a recap of their recent adventure on Skaro , where she and Ian risked their lives to save the Doctor and Susan from the Dalek s . She cites Ian ' s bravery in the Cave of Skulls . Her tirade is abruptly ended when she sees the cathedral clock the Doctor keeps in the console room has melted , a sight which horrifies her . They all check their watches and see the same has happened to their timepieces . The Doctor excuses himself from the room and returns with a tray of drinks , a " nightcap " which he serves as a peace offering to his companions . Barbara , Susan and Ian retire to their quarters and drink the nightcaps . After looking in on his companions to confirm they are asleep , the Doctor returns to the console . As he examines it , a pair of hands swing him around and grab him by the throat . The Brink of Disaster ( 2 ) . The Doctor ' s attacker is none other than Ian . A strange force has overridden the effects of the drug and compelled him to stop the Doctor from operating the TARDIS controls . Ian recognises the Doctor and collapses . Barbara enters and finds Ian and herself openly accused of sabotage by the Doctor . As Barbara tries to reason with the Doctor , Susan enters the room and sides with her grandfather , but then finds herself believing her teachers ' innocence . The Doctor threatens to put the humans off his ship ; suddenly an alarm sounds . The fault locator lights up , showing faults in every system . An explosion rocks the ship . The Doctor realises the TARDIS ' power source , located beneath the console , is trying to force its way out and they are only minutes from destruction . Faced with a common peril , the travellers forget their differences and begin to work together . Barbara deduce s that the strange events are an attempt by the TARDIS itself to warn the crew that something is wrong . The Doctor traces the problem to a broken spring in the fast return switch . The malfunction is causing the TARDIS to head back to the creation of a solar system ; the strange events were just the TARDIS ' attempts to warn its passengers before the ship was destroyed . Fixing the switch returns everything to normal . The Doctor apologises to Ian , who accepts straight away . Barbara needs more convincing but she is eventually won around by the Doctor . The foursome prepare to explore their new surroundings , this time a snowy planet . When Barbara and Susan go outside they discover a giant footprint in the snow . Home video and audio releases . DVD release . This story was released ( " Doctor Who : The Edge of Destruction " ) together with " An Unearthly Child " and " The Daleks " in " The Beginning " DVD box set . Special Features : Released : Box sets . This story was released along with " An Unearthly Child " and " The Daleks " in a box set called " The Beginning " . Digital releases . This story is available : Video release . This story was released as " Doctor Who : The Edge of Destruction and Dr Who : The Pilot Episode " as a compilation video . The BBC originally intended to release this story in a box set with " An Unearthly Child " and " The Daleks " , but they changed their plans and decided to release each story individually . Released : Notes : This video release includes the full takes of " The Pilot Episode " . The US release also included the documentary " The Missing Years " and episode 3 of " The Underwater Menace " .