 FACT: About 15 minutes into the movie, when Joseph Cotten is playing  poker, on his deal they are playing "Jacks or better" (meaning you  cannot bet your hand unless you have at least a pair of Jacks).  Joseph Cotten takes four cards on his turn. Since he only left  himself with one card he could not possibly have had at least a pair  of Jacks, so he shouldnt have been able to play the hand.