The chain

You just dropped off your child at the bus stop. A panicked stranger calls your phone. Your child has been kidnapped. The stranger then explains that their child has also been kidnapped, by a completely different stranger. The only way to get your child back is to kidnap another child; within 24 hours. Your child will be released only when the next victim's parents kidnap yet another child. And most importantly, the stranger explains, if you don't kidnap a child, or if the next parents doesn't kidnap a child, your child will be murdered. You are now part of The Chain.