10 Infamous Movie Plot Holes That Have Simple Explanations
6. How Did McClane Know "Bill Clay" Was Hans Gruber? - Die Hard
The "Plot Hole"
When Hans Gruber (Alan Rickman) affects an American accent and pretends to be a hostage by the name of Bill Clay, how did John McClane (Bruce Willis) know that he was actually a terrorist? Isn't that rather convenient deduction for a supposedly "regular" cop?
The Explanation
This apparent logical leap is caused by a small scene which was cut from the movie, in which Hans and his fellow terrorists synchronise their watches, revealing to the audience that the terrorists are all wearing the exact same timepiece.
And so, all is revealed to John when he offers a cigarette to "Bill," allowing John to see his wrist and notice that he's wearing the same time-piece as everyone else. In the words of co-writer Steven E. de Souza himself:
"When Bruce offers the cigarette to Alan Rickman, Bruce sees the watch. You see his eyes look at the watch. That's how he knows that he is one of the terrorists."