Summer (audio story)

 was a 2007 Big Finish Productions full-cast audio short story featuring the Fifth Doctor and Nyssa. It dealt with the problems that arose from the Doctor carrying anachronistic money around in his pockets during the time that Sir Isaac Newton was trying to catch counterfeiters in late 17th century England.

Publisher's summary
During the stifling heat of a summer past the Doctor and Nyssa suffer the vengeful wrath of Isaac Newton.

Plot
The Doctor and Nyssa once again finds themselves imprisoned in the Tower of London. The Doctor laments that he got them into hot water by being absent-minded as he accidentally gave Nyssa coins from the wrong eras to pay their tavern bill with. Unfortunately, Sir Isaac Newton happened to present in disguise at the tavern, and he promptly arrested the duo for forgery.

Isaac Newton then personally visits them in the cell, telling them that usually he has forgers summarily executed, but since he finds the design of the coins strange and have noticed they are made from metals he does not recognise, and he want answers. The Doctor tries to explain that they are travellers from far away and that is the reason for the strange coins, but Newton suspects there is more to it so he will keep them alive so they answer his questions.

Later that night, the Doctor and Nyssa are brought outside. Nyssa fears that it is an impending execution, but the Doctor assures her that such things are always done in public on Saturdays, so it must be something else. Instead they are place before Newton again, who shows them that he has found TARDIS and wishes to interrogate them alone. Having found that it is impossible to damage the TARDIS and having no other explanation for the design of the modern coins, and the fact that there is a genuine Roman coin and an even more futuristic triangle-shaped coin amongst them, Newton has deduced that the Doctor and Nyssa must be time travellers as well as aliens and the TARDIS their time machine. The Doctor and Nyssa tries to play dumb and explain that he is wrong and the TARDIS is merely a sedan chair, offering him to show it in the hope they can distract him and escape, but Newton gets entirely caught up in his deductions and for a moment plays them no mind as he analyses the coins, predicting amongst other things the American War of Independence, World War I, the Irish War of Independence, the Moonlanding, and the 22nd century Dalek invasion from them. Suddenly, snapping back to reality, Newton states that he believes the Doctor is travelling in time to gloat and views the past as "a series a trophies", and disgusted by this, he orders him and Nyssa imprisoned again.

Back in the cell the Doctor worries how much the timeline can polluted from all this. Borrowing Nyssa's ear-ring, he attempts to stage an escape by performing a parlour trick he learned from Houdini, in which a piece of lead appears to turn into gold, to impress and bribe the jailer, but it falls flat, as the jailer prefers his steady job, and him and Nyssa is again brought before Newton. Learning about the trick the Doctor tried to pull, Newton is equally unimpressed, stating that the Doctor is no alchemist as he would know the secret of transmutation if he where. This prompts Nyssa to explain to Newton that turning base metals to gold is impossible, but on the quantum level certain elements can become something else, though not gold. Impressed by her knowledge, Newton asks the guards to step back. Nyssa then goes on to explain who the Doctor is, telling about his status as outcast among his time travelling people, and how she met him, telling Newton that what he predicted might be true, but the Doctor was always there throughout history to help, while the Doctor tells Newton how much he respects him and of the impact he will leave on Earth's history.

Overloaded by this information, Newton starts groaning and twisting in response and the jailer notices that he is having one of his "funny turns" again, and advises the Doctor and Nyssa to let him cool down, but angrily Newton calls him a simpleton and orders him to leave, while demanding that the Doctor and Nyssa continue their tales from the future. The Doctor continues to extol Newton's legacy, telling him that continents on other planets and measurements of units will be named after him, and every child will learn of him in school, and this will go on for as long as England stands. Newton asks if this will be until the 22nd century invasion, which the Doctor confirms, telling him it was the best he could do. Newton says he believes they tell the truth, before having a seizure from the huge amount of information. Nyssa says it is their chance to escape and suggest they make a run for the TARDIS, but seeing Newton lying chocking on his own tongue, the Doctor refuses to leave him, saying that he will not allow a genius of Newton's calibre to die on his watch and tells Nyssa to run ahead.

The Doctor manages to calm Newton down from his seizure, and Newton laments how everyone is doomed to die and be forgotten. He asks the Doctor if they will ever meet again, to which the Doctor answers they will not. Satisfied with this, Newton tells him he is free to go and orders the guards to not let any harm come to him. The Doctor then rejoins Nyssa in the TARDIS, telling her that Newton will recover, and when he does he will be bored with the memory of them and move on to something new.

Cast

 * The Doctor - Peter Davison
 * Nyssa - Sarah Sutton
 * Guard - Jeremy James
 * Molly - Sunny Ormonde
 * Jailer - Trevor Littledale
 * Sir Isaac Newton - David Warner

The Doctor

 * Molly hints that a another incarnation of the Doctor was imprisoned in Tower of London a week before this story takes place.
 * Isaac Newton says that he became an alchemist because he was given a book by an old man who is implied to be the First Doctor.
 * In an attempt to appear like a magician the Doctor quotes "Who is the Doctor?"

Continuity

 * The Doctor expresses interest in visiting the Council of Nicaea one day, which he would later do in the company of Peri Brown and Erimem. (AUDIO: The Council of Nicaea)
 * The Doctor quotes a few lyrics from Who is the Doctor.
 * While imprisoned, the Doctor laments that he has not found the time to make a new sonic screwdriver since the original's destruction by the Terileptil leader in September 1666. (TV: The Visitation) The Seventh Doctor would eventually make a replacement. (AUDIO: The Dark Husband; TV: Doctor Who)
 * The Sixth Doctor would later be imprisoned in the Tower of London on two separate occasions in 1590 and January 1555 (AUDIO: Point of Entry, AUDIO: The Marian Conspiracy), whereas the Eleventh Doctor would suffer the same fate in the 17th century but managed to escape with an "invisible sphere" (TV: The Impossible Astronaut). The Eleventh Doctor was eventually imprisoned again, as were the War Doctor and Tenth Doctor, in 1562. Ironically, their prison cell door was left unlocked. (TV: The Day of the Doctor)
 * Isaac Newton mentions that his nose bled for three days after the apple fell on his head. The Fourth Doctor once claimed that he sat in Newton's tree dropping apples on his head and then explained gravity to him over dinner. (TV: The Pirate Planet)
 * The Tenth Doctor claimed that he had once taken Newton on a trip to Practas Seven, but he seemingly did not take the experience of travelling through time and space very well as he "sat in a corner and whimpered." (COMIC: Final Sacrifice)