In an unlikely case of truth proving stranger than fiction, the events in Sherlock - The Sign of Three are actually based on a real-life crime.
|Sherlock's best man speech. What could go wrong?|
Sherlock S03E02 - The Sign of Three
|Alfie Enoch as Private Bainbridge|
The concept of the case is a classic locked room mystery (Sherlock even refers to it as such upon finding Bainbridge's body). The method - the victim was stabbed by a very sharp blade that penetrated his uniform imperceptibly - fits neatly within the "fatal wound was inflicted prior to the victim entering the locked room" category. The Sign of Three offers a slight twist on this format by making the victim(s) unaware of their wounds (their tight fitting uniforms act as a tourniquet and prevent blood-loss while worn).
In 1898 Empress Elisabeth of Austria was assassinated using a very similar method. Italian anarchist Luigi Lucheni, feigning a stumble, bumped into the Empress and stabbed her with a sharpened needle file as she was about to board a steamship. The Empress collapsed, but was helped up to her feet and continued to walk the short distance to the boat and up the boarding ramp. Whilst onboard she lost consciousness, but revived after her lady in waiting cut the laces of her tightly fitting corset. The Empress said that she felt no pain, and enquired as to what had happened before collapsing once again.
|An artist's impression of the assassination. Source: Wikipedia|
More examples of locked room or impossible crime fiction imitating reality can be found here.