The Returning Twin
This plot line, or twist, has been used in many films and it is particularly popular in soap operas. Returning characters generally are used, for example Jock Ewing in Dallas. When it happens the rest of the cast are usually divided on whether it really is that person, with those in favour typically driven by hope. In most cases a returning character is a fake and that is revealed later.
In some of our scripts we use this device in our 'up our sleeve' category. We hold back clues and use them with certain groups when we need to up the game. An example of such a situation is where one person discovers an important clue and shares it with the whole room. Even in competitive team situations this can happen because the detective may be proud of his or her discovery. In this case we bring in extra clues to enhance the game, so everyone is not following the same solution.
A newspaper clipping in brought in covering the disappearance of the victim's twin when they were children, and one of the suspects is described as looking like the victim. People like neat solutions, so many will start to make up a story in which the suspect is the returning twin. We do not need to do this ourselves, it all happens of its own accord.
Lesson: Do not give neat solutions extra weight just because they seem to fit. Keep investigating.
The Serial Killer
Columbo, when asked why he solved all of his cases, observed that most murderers are amateurs. They are committing the crime for the first time, whereas he spent every working day solving crimes.
The one type of killer who breaks this rule is the serial killer. They tend to become more competent as they carry out their killings, because practice makes perfect. Investigators hope that they will become careless, or arrogant and start to make contact with those investigating their crimes.
How easy would it be for a murderer to kill someone and make it look like the work of an active serial killer to hide their dastardly deed. As investigators work on such cases they get closer and closer to the killer they are trying to catch. While they may not know the actual identity of the murderer they almost know them because they study everything that they do. Typically key information will be held back from the media, so copying without inside knowledge would be difficult.
However, it is an intriguing plot idea. Perhaps the murderer using this strategy is 'on the inside' in some way.