Summer ( audio story ) 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 , so instead he wants answers from them . 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 placed before Newton again , who shows them that he has found the TARDIS and wishes to interrogate them about it 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 deduce d 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 him the inside in the hope they can distract him and escape , but Newton gets entirely caught up in his deduction s 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 Moon landing , 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 begins to worry about how just much the timeline has been polluted from all this . Borrowing Nyssa ' s ear - ring , he attempts to stage an escape by performing a parlour trick he learned from Harry 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 are again brought before Newton . Learning about the trick the Doctor tried to pull , Newton is just as unimpressed as the jailer , stating that the Doctor is certainly 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 so they can speak in private . 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 Newton angrily calls him a simpleton and orders him to leave , while demanding that the Doctor and Nyssa continue their tales about 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 . Nyssa says she cannot understand why the Doctor would admire Newton so much , to which the Doctor responds that Newton ' s hidden talents greatly outweighs his less - than - ideal personality , to which Nyssa points out that the Doctor conjuring trick with the ear - ring was also a pretty impressive hidden talent . The Doctor then states he will now perform his next trick as he starts working the TARDIS controls .