His first film for the company, The Man Who Knew Too Much (1934), was a success and his second, The 39 Steps (1935), is often considered one of the best films from his early period.^[49] This film was also one of the first to introduce the concept of the "MacGuffin", a plot device around which a whole story seems to revolve, but ultimately has nothing to do with the true meaning or ending of the story. In The 39 Steps, the MacGuffin is a stolen set of design plans. Hitchcock told French director François Truffaut:

There are two men sitting in a train going to Scotland and one man says to the other, "Excuse me, sir, but what is that strange parcel you have on the luggage rack above you?", "Oh", says the other, "that's a Macguffin.", "Well", says the first man, "what's a Macguffin?", The other answers, "It's an apparatus for trapping lions in the Scottish Highlands.", "But", says the first man, "there are no lions in the Scottish Highlands.", "Well", says the other, "then that's no Macguffin."

http://en.wikipedia.org/wiki/Alfred_Hitchcock