First locating the Monk hauling a bag of money in the late twentieth century off the coast of Scotland before following him to twentieth second century Hong Kong and demands answers. When the Monk refuses to elaborate until he's finished his business in Hong Kong the Doctor joins him to a black market deal where, one Swiss bank account, an investment in Google, and a few centuries of compound interest later, the Monk is trading a bag of diamonds for a Smart Black Omnivariable Decryptor. The Monk then sedates the Doctor and makes a start on his real plan.
The Monk is being employed by the mysterious Mr Mallory in order to find and secure the Magna Graln in exchange for taking a bounty off of the Monks head, and has been infected with nanobombs that will kill him if he disobeys. The Monk is almost ready to enact his plan but needs one final, crucial component for his plan: Sarah Jane Smith!
The Doctor eventually tracks the Monk down to Glastonbury, 2012, where he also notices a bizarre energy signal in the sky. Feeling like this could be interesting, he goes to investigate and soon meets Brigadier Kate Lethbridge-Stewart and Patronella Osgood, who investigated the signal on their own and accidentally summoned a bipedal crocodile warrior, a member of the Hyreth, to UNIT headquarters. Not that it ends up being much of a threat, as it dies of old age soon after the Doctor arrives. Kate eventually realises that the Doctor shouldn't be here, as the headquarters had been made TARDIS proof, and the Doctor realises that the Monk is almost certainly using this opportunity to snatch up the Magan Gral, hidden in the Black Archive.
The Monk and Sarah arrive in the Archive and begin searching. He used the Decryptor to remotely activate a protocol that turned off the Archives security systems and is in fact searching for the Magna Gral. Sarah, who met the Hyreth before, was brought in by the Monk to find it since he doesn't actually know what it looks like.
The Doctor, Kate, and Osgood eventually meet Sarah, and after a brief reunion between the Doctor and Sarah they all go to the unconscious Monk (he was threatening her with a gun) and he finally explains his deal to the team. They decide to find the Magna Gral together to figure out what to do with it, and the Monk uses the opportunity to finally take it and leave, and remotely fries the Temporal Iterator in the TARDIS as he does. Osgood remembers that the Doctor was trying to work on one before, and takes them all to her house (she likes to take her work home).
While waiting for Osgood to find the prototype Iterator the Doctor and Sarah have a frank discussion about whether or not he really remembers her all of these lives after they parted, and the Doctor soon realises that it's possible he may cease to be if he continues to degenerate. Osgood eventually finds the device and the gang set off to find the Monk once more.
The Monk reunites with Mr Mallory and hands him the Magna Gral, and only realises after slagging the Hyreth off as "nutters" that Mr Mallory is actually one of them, real name Galavaunt. Before Galavaunt can kill the Monk the Doctor arrives and discovers that the Hyreth have never forgiven the Doctor for stealing the Magna Gral. Galavaunt soon departs with the Monk, and the crew make chase to the Hyreth warship.
On their ship the Monk notices that the ship's only being manned by two people, Galavaunt and Baravoar. They're biding their time until they can mount a proper attack on the Earth, and only then will they awake their numbers from slumber. The Doctor, meanwhile, realises that the ship is cloaked to avoid TARDIS materialisation and decides the best course of action is ramming speed.
Once in, the Doctor and Sarah make a beeline to try and find the Monk, much to the protest of Kate and Osgood who are quite concerned about the whole invasion that the Hyreth are planning. They eventually find the two Hyreth's about to awaken their army but the Doctor's plan is interrupted by Kate and Osgood confronting the Hyreth. In the ensuing scuffle Galavaunt awakens his people, only for all of them to die of old age as soon as they are roused form their slumber. Galavaunt, distraught at the death of his people, decides to abandon their invasion and try to figure out what to do next.
The Doctor removes the nanobombs from the Monk, Kate and Osgood see to getting the remaining Hyreth to a home for refugee aliens, and Sarah asks that the Doctor take one laat trip with her to drop her home. The Doctor refuses, as he is still suffering degeneration, but the Monk is more than happy to drop her off if it means he gets to leave. Before he does the Doctor asks him about degeneration weapons, only to discover that he's found the Monk before whatever happened to him and as such he has no idea what's happened.
Though, the Monk does suggest that if he needs some stabilising for his condition, then he could probably get a DNA match from his lovely daughter. And so with one last goodbye to Sarah as the degeneration continues to affect him, the Doctor sets off to find his daughter.
Tropes
- The Cameo: It's a 60th anniversary celebration, what'd you expect? This episode features all of the first seven Doctors making fully voiced cameos at the start as the degeneration sets in. The Eighth Doctor note is also technically present, but as he's basically unconscious at the start of the adventure he doesn't speaknote .
- Remember the New Guy?: The Hyreth, the main alien menace of the story, are treated as prior foes of the Doctor and Sarah and are heavily hinted to have encountered them during the Third Doctor's era. Much like Timelash, this adventure has never actually been depicted before and we just have to take their word for it.
- Shout-Out: The story is filled with Call Backs and Shout Outs to the series history but special mention should be made about how the Monk's code name to Mallory/Galavaunt is Thelonious.
- 20 Minutes into the Past: The story is generally set in the early 2010's, though writer Robert Valentine sets it more specifically as a year or two before the fiftieth anniversary in 2013.
