I'm Calling From the Police

You get a call in the middle of the night - the person tells you they are with the police, and your son or grandson has been arrested.  If you don't give them a credit card to pay his bail, he will have to spend the night in jail (or worse).  This is a scam.  The police will never call and demand a credit card over the phone for bail money.  The person on the other end counts on you being half-asleep, and in a panic, in order to get your credit card information.