History Literature / TheThinkingMachine

* TwinSwitch: In "Convict #97", a convict escapes by forcing his twin brother to take his place on the cell. Van Dusen works out what has happened because the brother's have different shoe sizes.

* AnimalAssassin: In "The Problem of the Grip of Death", a man in found strangled in a [[LockedRoomMystery locked apartment]]. He was actually strangled by a boa constrictor, that entered through a rat hole in the wall. (Strictly speaking this a case of bizarre death by misadventure rather than murder, but it plays out like a murder.)

* ThievingMagpie: In "The Rosewell Tiara'', Van Dusen investigates when a single diamond is stolen from a tiara inside a locked safe. The 'thief' turns out to be the owner's pet cockatoo, who has a penchant for shiny objects and who plucked out the diamond and swallowed it. How the safe came to be opened turns out to a completely separate mystery.

* LockedRoomMystery: The stories contain multiple variants on the locked room mystery. "The Problem of the Grip of Death" is an excellent straight example where the victim is found strangled in his locked apartment, with the windows latched and the door not only locked, but barred in such a way that the bar could noy have been dropped from the outside. The solution ultimately involves [[spoiler:a boa constrictor acting as an AnimalAssassin]].

* DisguisedInDrag: In "Convict #97", two brothers perform a TwinSwitch. The innocent twin enters his brother's cell disguised as their (non-existent) sister. In the cell, the brothers swap close, and the convict exits in the 'sister's' garb.

* LockedRoomMystery: stories contain multiple variants on the locked room mystery. "The Problem of the Grip of Death" is an excellent straight example where the victim is found strangled in his locked apartment, with the windows latched and the door not only locked, but barred in such a way that the bar could noy have been dropped from the outside. The solution ultimately involves [[spoiler:a boa constrictor acting as an AnimalAssassin]].

* TheConvenientStoreNextDoor: In "The Problem of the Deserted House", criminals rent an old, abandoned house and, over the course of several months, construct a tunnel from the cellar to a bank vault (crossing a subway tunnel in the process), so they will have the secret passage in place with a shipment of several million dollars in gold arrives.

* CouldntFindAPen: In "The Problem of Cell 13", Van Dusen manages to send messages from inside the condemned cell by scraping shoe polish off his shoes and using the metal aglets of his shoelaces as a stylus.

* TheConvenientStoreNextDoor: In "The Problem of the Deserted House", criminals rent and old, abandoned house and, over the course of several months, construct a tunnel from the cellar to a bank vault (crossing a subway tunnel in the process), so they will have the secret passage in place with a shipment of several million dollars in gold arrives.

* SherlockScan: Not Van Dusen's usual stock-in-trade, but in "My First Experience with the Great Logician", he is able to deduce that his patient's name, address and profession; that he smokes; that he is wearing his clothes for the first time that winter; that he was widowed a few months earlier; that he kept house then; and that the house was infected with insects.

* SherlockScan: Not Van Dusen's usual stock-in-trade, but in "My First Experience with the Great Logician", he is able to deduce that his patient's name, address and profession; that he smokes; that he is wearing his clothes that winter; that he was widowed a few months earlier; that hr kept house then; and that the house was infected with insects.

-->"And, gentlemen, if I had been killed one of the most valuable mind in the sciences would have been lost. It would have been nothing less than a castastrophe."

* InsuferableGenius: Professor Augustus Van Dusen, Ph. D.,LL. D., F.R.S. M.D. M.D.S, etc., a.k.a. 'the Thinking Machine'. After neatly being killed in "The Problem of the Deserted House", he remarks:

* SuicideNotMurder: In "The Great Auto Mystery", a woman is found stabbed to death in the front of an open air automobile. It is ultimately revealed that woman was the one everyone thought she was, that the death was really suicide, and that one of the passengers knew the truth but could not say anything as it would have raised a large number of awkward questions.

* InspectorLestrade: Detective Mallory is this to Professor Van Dusen. Van Dusen seems to respect Mallory, regarding him as a decent, if plodding detective. Mallory varies between welcoming Van Dusen's involvement in his cases, or regarding him as an irritating intrusion. While Mallory is quite capable of handling ordinary crimes, he is out of his depth in dealing with the 'impossible' crimes Van Dusen specialises in: either becoming totally flummoxed or simply arresting the most obvious suspect.

* AmateurSleuth: Van Dusen is a university professor who solves 'impossible' crimes brought to him by his journalist friend Hutchinson Hatch. Van Dusen receives no financial renumeration for his efforts; merely the satisfaction of proving that nothing is impossible.

* CatchPhrase: Van Dusen is fond of saying "Two and two makes four, not sometimes but always".