[Quick Summary: Margaret Ford, a female psychiatrist, falls for a Mike's con, and becomes entrapped in his elaborate crime web.]
Mike tells Margaret that the "confidence game" works because the mark doesn't give the confidence.
The con man gives his confidence to the mark, usually by bringing the mark in on the scheme.
Mike does it again and again to Margaret.
ex. At their first meeting, he asks her to help him, and she loses her bank account.
ex. Mark develops Margaret's trust by showing her how the game works on a young man at the Western Union office.
ex. His cronies show her how the Tap con works.
The script ups the ante with each demonstration. Margaret feels "in", accepted, and somewhat invulnerable.
The last thing on her mind is that these nice guys were setting her up...and BOOM! That's when it happens.
WHAT I'VE LEARNED: The stakes rise beautifully as Mike confides more and more in Margaret.
Also, the false sense of security is a great setup for a great third act payoff
House of Games (1989)
Written & directed by David Mamet