Serpent in the Silver Mask (audio story)

Serpent in the Silver Mask was the two hundred and thirty-sixth story in Big Finish's monthly range. It was written by David Llewellyn and featured Peter Davison as the Fifth Doctor, Matthew Waterhouse as Adric, Sarah Sutton as Nyssa and Janet Fielding as Tegan Jovanka.

Publisher's summary
You are cordially invited to Argentia, the galaxy’s most exclusive tax haven, to attend the funeral of mining magnate Carlo Mazzini. The memorial service will be followed by music, light refreshments, and murder!

Carlo's heirs have come to say their final goodbyes (and find out how much they’ve inherited) but when a masked killer begins picking them off one by one, Argentia goes into lock-down, closed off behind its own temporal displacement field.

Can the Doctor, Nyssa, Tegan and Adric apprehend the murderer before Argentia – and everyone on board - is forever cut off from the rest of the Universe?

Part one
The TARDIS lands on Argentia, a luxury space station temporally displaced sixty minutes outside of time to avoid tax, for the Doctor to collect diothanine crystals to make a new sonic screwdriver. Without the necessary papers, Superintendent Galgo takes the four travellers' DNA for a bioscan and directs them to the funeral of Carlo Mazzini, executive officer of the Mazzini Mining Company. They meet his family of demi-clones: his son Angelo, brother Francesco, sister Maria and nephews Joe, Peter and Paul.

Sofia Cozzi, the executor of Carlo's estate, reads out the will bequeathing everything, including 9,000,000,000 credits, to Angelo. The Doctor and Adric follow him to the sync pods to collect diothanine crystals, although all but one have seemingly been wiped out by a temporal anomaly, and Adric sees Angelo killed by somebody in a silver mask and a black hat with an incineration beam. Galgo puts Argentia under lockdown after confirming that the ash in the pod belongs to him and Joe points out to Tegan that Francesco, the next in line, was not with everyone else during the murder. However, Francesco has been killed by the bite of a reptilian arthropod.

Part two
The Doctor and Galgo kill the reptile and save Tegan, but it sprays Galgo with its nerve toxin and he requires medical attention. Dissecting the reptile, the Doctor is unable to identify its species and sends Nyssa to the TARDIS to investigate whilst he and Adric examine Carlo's villa where Angelo was staying. The Doctor suspects that the inheritance might not be the sole prize of the killer upon finding that a painting that Angelo saved from 1944 has been stolen and sends Adric to help Nyssa before visiting Galgo.

Joe tells Tegan that Maria, the next in line, is unlikely to be the killer but her cosmetics company on Suganda is rumoured to be nearing bankruptcy. Nyssa identifies the reptile as a Sugandian Normic and the Doctor goes to see Maria, who accuses Sofia of being behind the killings and professes her own innocence. Being between marriages, she attempts to seduce him and dies suddenly. Galgo examines the crime scene and detects the fast-acting poison hydroxatine in Maria's system and arrests the Doctor on suspicion of the three murders.

Part three
After visiting the Doctor in his neutron field cell, Adric finds a ventilation system in the villa which he suspects was used by whoever stole the painting, although Sofia is doubtful, and flees from discarded Baby Chuckles to a karaoke bar where he is joined by Galgo. They come across the corpse of Tom Rossi, Carlo's previous assistant. Nyssa joins them after discovering that a biomechanical drone injected Maria with the hydroxatine and they go to search Paul and Peter's room at the Hotel Excelsior, finding Paul dead and heading into the ventilation system to locate Peter.

Tegan, now suspicious of Joe, updates the Doctor on the investigations and goes to inform the others when he deduces that the murderer is using knowledge gained by time travel. Meanwhile, the group corner Peter, who claims that he killed Paul by accident whilst fighting over the painting but denies having stolen it or being behind the murders. Before he can elaborate further on the painting, he is killed by a figure with a cryo-blaster and the group run after the killer. They trap the killer above the oxygen gardens and Tegan and Sofia arrive, but Sofia draws a gun and reveals that she has been working with the killer. They overload the turbine and the group hold on to stop themselves being sucked in.

Part four
Suddenly, the TARDIS arrives and the Doctor manages to rescue them, explaining that he managed to logically convince Bernard, the robot guarding his cell, that it was impossible for him to have committed the murder and Bernard released him. They explain to him that Sofia was an accomplice of the killer but the Doctor explains that due to his time sitting alone in the cell and working it out with Bernard listening, he managed to deduce that and has also figured out who the killer is. Tegan thinks it's Joe's but the Doctor's explains it can't be and she rushes off to warn him despite the Doctor warning her to come back. He then takes Nyssa and Galgo to the lower levels where the time ships are parked. Tegan learns from a service bot that Sofia is in the Mazzini's villa where Joe is headed and heads there himself while the Doctor, Nyssa, Adric and Galgo find a vehicle in the lower levels that shouldn't be there.

Tegan finds the villa deserted and follows the sound of strange music into the house, and finds Joe tied up and he reveals it was a trap for them both. The killer confronts Tegan and reveals its plan to use the two as hostages when suddenly a Baby Chuckles comes into the room. The killer blasts it to smithereens but more arrive and attack the killer for destroying one of them. Distracted, the killer gets captured and the Doctor, Nyssa, Adric and Galgo reveal themselves and explain they had used the dolls as a distraction. They take off the killer's mask and find out it's Angelo Mazzini. The Doctor explains that he checked the logs of Angelo's ship and found that Angelo had done something illegal and travelled along his own personal timestream ten years forward. Angelo explains that he wanted to see what would happen after inheriting such a massive amount of money and reveals that the family all end up murdering each other in an attempt to claim the inheritance leaving Paul and Peter unscathed and inheriting it and Angelo explains his disgust at such idiots possessing his father's wealth. When Adric asks about Angelo killing himself, the Doctor realises that this is to his advantage because once he was registered as deceased on Argentia's systems, he would no longer be tracked and registered and would be free to move about the station undetected. He had used the painting as a scapegoat to frame (pun is acknowledged in the story) his family as well. Adric asks about that creating a paradox but the Doctor realises that since Argentia is in lock-down it is in a separate time and so the paradox is being held at bay. Just then, Angelo takes Adric hostage and communicates with Sofia to beam them aboard their escape ship, and they are teleported away. The Doctor explains they need to get to the field generator quickly.

Adric asks how they'll escape and Sofia explains that they've engineered a wormhole and are currently attempting to align the temporal drives, while Angelo mentions how good Sofia is with this "stuff". The Doctor and crew arrive on the control deck and look for the field fabricator. The Doctor explains someone broke in and created a quantum tear, causing a wormhole that he explains after being sealed would cause Argentia to be completely cut off in time trapping everyone inside. Galgo thinks all hope is lost but the Doctor explains that they can use the diothanine crystal to seal the quantum tear, however, he laments that he should have realised earlier what was going on when he explored the mine and only found the one, explaining that the other crystals must've been disintegrated by the quantum tear. They manage to stop it but the Doctor explains that Angelo still has Adric and if he leaves Argentia the paradox will catch up with him. Galgo retorts he is fine with it killing him but the Doctor, claiming he is not judge, jury and executioner, believes Angelo should be tried on Argentia instead. They take off to find him.

The Doctor locates Angelo's ship and tries to get him to open up and they open a communication channel and the Doctor explains what he did, telling Angelo that if he leaves the station, the paradox will catch up with him and he will be disintegrated just as he did to himself earlier. Angelo believes the Doctor to be bluffing, but when he asks Sofia, she is distraught as she simply doesn't know. Adric tries to convince him that the Doctor is not someone who would lie about such a thing, but Angelo ignores him and takes a chance and tries to escape, only to end up disintegrated and Sofia in tears. The Doctor, Galgo, Nyssa and Tegan get aboard and Galgo places her under arrest.

In the aftermath Galgo apologises to the Doctor for accusing and locking him up which the Doctor brushes off, and Tegan sadly parts ways with Joe, despite his offer to stay with him as he has now inherited Carlo's fortune, saying that although tempted by his offer, she wants to spend more time with her friends.

Cast

 * The Doctor - Peter Davison
 * Adric - Matthew Waterhouse
 * Nyssa - Sarah Sutton
 * Tegan - Janet Fielding
 * The Mazzini Family - Samuel West
 * Superintendent Galgo / Zaleb 5 - Phil Cornwell
 * Sofia Cozzi - Sophie Winkleman

Continuity

 * Tegan mentions she was a stewardess. (TV: Logopolis et al.)
 * When Adric asks the Doctor why he doesn't just ask the proper channels of communication for a diothanine crystal, the Doctor explains that that sort of thing usually results in a firm "no", just like "Can I play near the waterfall?", "Can I join the Time Lord Academy?" or "Can I borrow that TARDIS?" (TV: The Day of the Doctor et al., AUDIO: The Beginning, et al.)
 * When trying to open a door, the Doctor claims that now would be a good time to have the sonic screwdriver. (AUDIO: The Crimes of Thomas Brewster et al.)
 * Agatha Christie and her novels are known in places as far out as Argentia. The Tenth Doctor and Donna Noble would later meet her themselves. (TV: The Unicorn and the Wasp)
 * The Doctor mentions to Maria Mazzini that he is a Time Lord. (TV: The War Games et al.)
 * Maria claims the Doctor has "powerful thighs" while attempting to seduce him and asks if he does a lot of running. Many people explain that there is a lot of running involved when it comes to travelling with the Doctor, as mentioned by, for example, Donna Noble. (TV: The Doctor's Daughter)
 * The Doctor, while talking to the robot guard Bernard in his neutron field prison cell, talks about how countless times the people under his care have "grown up" and "left the nest". He refers to the many companions who decided to stop travelling with him and go off on their own to start their lives, such as his granddaughter Susan, Vicki, Ben and Polly, Victoria, Jo Grant and many others. (TV: The Dalek Invasion of Earth, The Romans, The Faceless Ones, Fury from the Deep, The Green Death et al.)
 * The Doctor also mentions to the robot how he was once exiled to and stuck on Earth for a time and that the UNIT canteen was disgusting. (TV: The War Games, Spearhead from Space et al.)
 * Adric, while being confronted by the Baby Chuckles dolls says, "Sorry, must dash", something the Fifth Doctor would sometimes say. Angelo also uses this line later while escaping their interrogation. (TV: The Five Doctors et al.)
 * When Tegan and the Doctor discuss the possibility that Joe might be the culprit, they each, talking out loud, go off on their own tangents, only to snap back to attention when each yells at the other "Have you been listening to a word I said?". The third Doctor and Jo had a very similar exchange on her final days working for UNIT. (TV: The Green Death)
 * The Doctor, upon discovering Angelo's ashes, when he attempts to escape Argentia, says "Ashes to ashes, dust to dust". He later uses the same line after tormenting the renegade Dalek Supreme that ends up killing itself. (TV: Remembrance of the Daleks)
 * Nicky Newman's Intergalactic Song Contest entry song is heard in the Karaoke bar Adric and Galga fall into. (AUDIO: Bang-Bang-a-Boom!)
 * Maclintock's Candy Burgers (TV: The Beast Below) and Henrik's Department Store (TV: Rose) are mentioned by Zaleb 5.