Stop the Pigeon (short story)

Summary
The Doctor and Ace investigate a missing tree in a housing development in Croydon, but Ace is attacked by a terrified man who's been transported through time twice for no reason he can think of. At that moment a talking pigeon arrives and transports both Ace and the man, Joe Dakin, through Time. The pigeon is part of a Virgoan probe, an emissary of a species of biomechanical shape-shifters who travel the galaxy trying to sort out temporal irregularities, and Joe Dakin is just such an irregularity. To make matters worse, the Virgoan probe was infected by a Krynoid while on Melandra IV, and the Krynoid part is beginning to become dominant and causing plants to come to life throughout Croydon as the probe struggles to fight off the infection. Meanwhile, Ace and Joe find themselves eighty years in the future, where it turns out Joe is originally from this time zone; he's been hypnotised and sent back in time by the Master, who claims to have developed a process of restoring the elderly to youth. In fact, he's been imprisoning the elderly and draining their bodies of nutrients in order to reverse his own mutation which he picked up on the Cheetah world, and he's been sending people back in time to kidnap the old people as babies in order to convince the public that his process works. The Doctor arrives with the pigeon, and sends Joe and Ace back in time to use the Master's equipment to separate the Virgoan probe and Krynoid pod and send the Krynoid pod forward in time to the Master's base of operations. The plan goes wrong, however, when Joe slips back under the Master's conditioning and attempts to kidnap a baby, and in the confusion Ace accidentally transports herself, Joe, and both the pod and probe forward in time. The confusion provokes a final struggle between the probe and pod, and machinery and plant life throughout the "retirement home" comes to life, destroying the Master's operation. The Master succumbs to the stress and nearly transforms into a Cheeta while trying to kill the Doctor, but he regains control of himself and kills the last of the old people he's kidnapped in order to stabilise his condition. The Doctor tries to use the Master's equipment to expel the Krynoid pod into the time vortex, but just in time the Virgoans get the upper hand, transform themselves into vegetable matter and absorb the Krynoid into themselves. The Master flees, leaving the Doctor to sort out the mess he's left behind him.

Characters
 * Seventh Doctor
 * Ace
 * The Master
 * Uses the alias Doctor Howard Chithros


 * Joe Dakin
 * Garth

Continuity

 * Krynoids first appeared in DW: The Seeds of Doom.
 * The Master still being infected by the Cheetah Virus contradicts NA: First Frontier.

Timeline
For the Doctor:
 * This story occurs after TN: Citadel of Dreams
 * This story occurs before ST: Ace of Hearts

For the Master:
 * This story occurs after
 * This story occurs before