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 makes some apologies for his behaviour..
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 to mysteriously open and close whenever Ian moves towards them. When Susan tries to operate the controls, she suddenly faints. As The Doctor revives, Barbara tends to him while Ian carries Susan to her room. There she tries to stab him with a pair of scissors, but suddenly bangs the scissors on the bed multiple times, 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, with some force from Barbara.
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, but it has also 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 begins to accuse their human companions of sabotage to get the TARDIS back to England in 1963. Furious, Barbara 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 Daleks, and 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. The travellers all check their watches and see the same has happened to their timepieces. Barbara, disturbed, takes off her watch and throws it away from her, before breaking down into tears.
The Doctor excuses himself from the room – but 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 accused of sabotage by The Doctor.
As Barbara tries to reason with The Doctor, Susan enters the room and seemingly side with her grandfather, but then believes her teachers’ innocence. The Doctor threatens to put the humans off his ship, this is stopped when suddenly an alarm sounds. The fault locator lights up, showing faults in every system. After panic enseeps the travellers, 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 deduces 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 – but Barbara needs more convincing and moves outside, where The Doctor and Ian banter before the TARDIS dematerialises. The Doctor then apologises to Barbara, who accepts his plea. The foursome prepares to explore their new surroundings, this time a snowy planet. When Barbara and Susan go outside, they discover a giant footprint in the snow….