10 Most Satisfying Twists In Star Trek
6. Computer, End Program
The estate of Sir Arthur Conan Doyle was not massively impressed when Star Trek produced Elementary, Dear Data. That is to say, while they wrote to the show and expressed their enjoyment of the episode itself, they had to remind the producers that Sherlock Holmes was not in the public domain, and was not free for use. Whoops.
Though it took another four years or so to wrangle out the details, Professor James Moriarty, as played by Daniel Day, returned once again in The Next Generation's sixth season episode, Ship In A Bottle. This time, the sentient hologram was accidentally activated by Reginald Barclay - the once admitted holo-addict.
What follows is an episode akin to a game of cat-and-mouse, where Moriarty once again holds the ship hostage as he seeks for his own happy ending. Picard, Barclay and Data do what they can to appease him, but it is clear that the genius program has the upper hand. He is able to leave the holodeck by willing it to happen, something that should have been impossible! It is only when is given a shuttle and guaranteed safe passage, with his companion the Countess Regina Bartholomew, that he releases control of the Enterprise again.
At which point it is all revealed to have been a clever simulation, created by the Enterprise crew as a ruse. It is a wonderful twist ending, though the most satisfying moment of the episode comes from the final check, where Barclay looks up and tentatively says 'Computer, End Program', with nothing happening. A beautifully cathartic ending.