The Beast of Kravenos (audio story)

 was the first story in the sixth series of The Fourth Doctor Adventures, produced by Big Finish Productions. It was written by Justin Richards and featured Tom Baker as the Fourth Doctor, Lalla Ward as Romana II, John Leeson as K9 Mark II, Christopher Benjamin as Henry Gordon Jago, Trevor Baxter as George Litefoot and Conrad Asquith as Percival Quick.

Publisher's summary
A stunning new star act is wowing the audiences of the New Regency Theatre. The modern mechanical marvel of canny canine charisma - the automated dog that can answer any question - the incomparable - the unbeatable - K9!

The Doctor and Romana have returned to Victorian London and been reunited with their old friends Professor George Litefoot and Henry Gordon Jago. However this is not merely a social visit. A terrifying crime spree is sweeping the capital, and the burglaries of 'The Knave' defy all logic.

Something impossibly dangerous is taking place amid the fog. Only the time travellers and their friends can stop it... but can they be sure they're all on the same side?

Part one
London, the 1890s. The Doctor, Romana and K9 are staying in the Doctor's Baker Street apartment while they investigate unusual energy pulses centred around the New Regency Theatre. They are assisted by Jago and Litefoot, who suspect one of the current season's performers may be behind it all.

Meanwhile, the police are investigating a series of seemingly impossible thefts committed by a thief nicknamed The Knave, who has the knack of stealing precious items from locked rooms without breaking in.

At the same time, a body turns up in the mortuary, which has been mutilated by some kind of large beast prowling the streets.

The Doctor and Jago track the energy pulses to a secret room underneath the theatre, where Jago is accosted by an unseen assailant before both Jago and his assailant are transported away by a transmat device.

K9 is able to trace a disorientated Jago to the residence of one Sir Nicholas Asquin. Asquin isn't home, but the Doctor leaves a calling card inviting Asquin to meet the Doctor at Baker Street. Asquin later accepts, and seems taken with the presence of the TARDIS parked at the apartment.

Meanwhile, the effect of travelling by transmat is having a nasty effect on Jago, who, in the presence of Romana, K9 and Litefoot, starts to transform into a beast. Luckily, sedation seems to halt and reverse the process.

The Doctor suspects that whoever is using the transmat is also the one behind the spate of thefts. The team set up a red herring in an effort to lure The Knave into a trap, but the bait isn't taken. Something else is stolen however - the TARDIS!

Part two
The Doctor suspects Sir Nicholas Asquin is the Knave and confronts him at his residence.

The Doctor's suspicions are correct. Asquin has been committing the thefts using the transmat - a piece of alien technology from the planet Kravenos he happened to discover lying about.

But due to the transmat being designed for Kravenon biotdata, repeated use by humans has both an addictive and transmogrifying effect, meaning Asquin is also the beast that has been terrorising London.

Unless the Doctor can find a missing component to the transmat, that he can use to change the settings to accept human DNA, the transmogrifying effects will soon become permanent.

Asquin begins to mutate again, so the Doctor detains him - idiotically in the room also containing the transmat. Asquin uses it to escape to an opium den, where he hopes the opium's extreme sedative effects will be enough to cure his lycanthropy.

The missing component to the transmat is located, enabling both Jago and Asquin to be cured - but not before Asquin runs amok at the opium den.

Asquin agrees to return the items he stole while under the effects of the Kravenos transmat, which is safely stowed away under lock and key.

Cast

 * The Doctor - Tom Baker
 * Romana - Lalla Ward
 * K9 - John Leeson
 * Henry Gordon Jago - Christopher Benjamin
 * Professor George Litefoot - Trevor Baxter
 * Inspector Quick - Conrad Asquith
 * Sir Nicholas Asquin - Ed Stoppard

Worldbuilding

 * The Knave is called so because he always leaves a playing card during his thefts.
 * The Kravenin are savage creatures, covered in hair and possessing sharp teeth and claws.
 * Their transmat technology uses nucleonic energy and is mildly telepathic: the more Asquin uses the transmat, the better he understands how to operate it. However, the transmat contains the biodata imprint of Kravenin, so when humans are transported, it reassembles their cellular structure based on Kravenin DNA, causing them to mutate.
 * The transmat relay is part of the larger system, and can transport the user within a 153 mile radius.
 * Jago doesn't know what a metre is, being only familiar with imperial measurements like yards and feet.
 * K9's stun gun has a level 3 setting, from which people can recover.
 * Litefoot refers to the fog as a real "pea souper."
 * K9 can track the TARDIS if the coordinates programmer is left active.
 * The Doctor and Jago help themselves to brandy.
 * K9 describes opium is a drug produced from the poppy plant, used as a narcotic, stimulant, intoxicant, and sedative.

Continuity

 * Jago refers to how unusual it is that the Doctor has two female friends with the same unusual name. (AUDIO: The Justice of Jalxar)