three-card trick 
noun [mass noun]
A game, traditionally associated with confidence tricksters, in which bets are made on which is the queen among three cards lying face downwards.He called the whole thing: ‘The best three-card trick I've seen in a long time.’...
- We should not fall for the propagandist's three-card trick, which as Aldous Huxley put it is to ‘make one set of people forget that certain other sets of people are human’.
- What these businessmen have somehow managed to do is pull off is possibly the most audacious and lucrative three-card trick in history.