foul balls

Question
If a ball is hit foul and a fielder almost catches it, but drops it, can the runner stay on the base they advanced to or do they need to return to their previous base.

Answer
Charlotte,

A foul ball is a dead ball and the runners can not advance.  

If a runner has advanced to the next base by the time the ball is called foul, then yes, they must return to the base they were on at the time of the pitch.

Thanks for the question.

Tom