Time-Flight - Plot

Plot

The TARDIS crew - the Doctor, Nyssa, and Tegan - are still mourning the loss of their former companion Adric (from Earthshock) when the TARDIS materialises at Heathrow airport in contemporary times and disrupts flight patterns. After clearing up his name, the Doctor is enlisted by Department C19 to track down a missing Concorde, Golf Victor Foxtrot, and its crew and passengers after it suddenly disappeared on approach into London.

The TARDIS is loaded aboard a second Concorde, Golf Alpha Charlie, and the Doctor and his companions meet Captain Stapley and his crew. Stapley pilots the Concorde to follow the same flight path as Victor Foxtrot, and appears to land safely back at Heathrow. However, the Doctor, monitoring the flight in the TARDIS, reveals they have fallen into a time contour, and are 140 million years in Earth's past; a strong psychokinetic field is projecting the illusion of Heathrow to the humans. Outside, they spot Victor Foxtrot, its crew and passengers under the assumption they are at Heathrow. However, they are performing slave labor under the control of Plasmatons, humanoid blobs of protein held together by the psychokinetic field.

One of the passengers, Professor Hayton, reveals he had seen through the illusion, and explains that a mysterious Oriental-like mystic named Kalid is controlling the psychokinetic field from a nearby Citadel, brainwashing his fellow passengers to try to break into a central chamber contained at the Citadel. As they learn of these events, they observe the passengers taking the TARDIS back to the Citadel.

As the group approaches the Citadel, Nyssa develops an empathic connection with the energy source, and Kalid erects a psychokinetic shield around her, preventing her from moving. As Tegan stays with her, the others continue on. At the Citadel, the Doctor goes off alone to find Kalid, learning that the mystic is seeking to gain direct access to a power source within the central chamber. When Stapley and Hayton start to disrupt Kalid's control on the passengers, Kalid redirects his psychokinetic field to enforce the illusion; this causes the field around Nyssa to fall. Nyssa and Tegan continue to the Citadel. Due to Nyssa's empathy, the two are able to enter the central chamber without obstruction. Nyssa, acting on instinct, throws an artifact into a large object in the chamber, causing a surge of power that disrupts Kalid's energy source, revealing him to be The Master.

The Master explains that he barely escaped from their last encounter (Castrovalva), his TARDIS damaged in the journey. Now stuck here in Earth's past, he seeks to use the power source in the central chamber to power his TARDIS and escape, and erected the time contour to obtain the passengers and crew of Victor Foxtrot to break into the chamber. The Master uses the Doctor's TARDIS to try to access the central chamber directly, while the Doctor, along with Hayton, find that the passengers have successfully broken through, and enter the chamber directly, rejoining with Nyssa and Tegan. They find that the energy source is really a gestalt intelligence of a great number of members of the Xeraphin species; their species were targeted in the crossfire between two other warring species, and they had tried to escape, but instead crashed to Earth, where the radiation of their damaged ship wracked their bodies, forcing them to take the ethereal form within the gestalt. They had constructed the Citadel to house the gestalt until the radiation had waned. However, when the Master arrived, his presence caused the gestalt to become unstable and causing a split personality within it, one evil side willing to help the Master, the other good side seeing his villainy and trying to stall the Master's actions.

The Master finds he is unable to access the central chamber with the TARDIS, and instead creates an induction loop to transfer the gestalt to his own TARDIS with the aid of the evil part of the gestalt. The Master attempts to leave but finds several parts of his TARDIS missing, taken earlier by Stapley and his crew, and though he replaces them with some from the Doctor's TARDIS, still lacks a critical temporal limiter. The Master offers a deal with the Doctor for a temporal limiter in exchange for the other parts he took and releasing the humans from his control. After installing the device, the Master departs in his TARDIS. The Doctor quickly instructs the humans to return to Alpha Charlie, and then uses his TARDIS to guide the aircraft back to contemporary times at Heathrow. The Doctor explains that he had programmed the temporal limiter so that the Master's TARDIS arrived later than his, and materialised his TARDIS where the Master's TARDIS would appear. As they observe, the Master's TARDIS fails to materialise and is bounced to an alternate destination – modern-day Xeraphin, where he would likely face the wrath of that species.

After ascertaining that the passengers and crew are safe, the Doctor and Nyssa return to the TARDIS and dematerialise, believing that Tegan is finally at Heathrow as she wanted. However, Tegan runs out of the airport too late to catch them, upset at being left behind.