The part to watch for is just before they begin the lighting of the lighter. The third party, the umpire, asks the gambler if he's really willing to go through with the extraordinary bet. Steve McQueen just looks down at his cocktail, looks down and toys with his olive. He doesn't look up at all and just says, "Yeah, I want to go through with it". For such a young actor barely at the beginning of his career, facing two much more experienced performers, along with his wife. To have the sheer confidence to deliver his line like that, not looking up from his glass, with such extraordinary power. This man was truly a megastar in the making.