Would I be in trouble if I refused to release custody back to them when I get my son this Friday for my visitation?

My child's mother was placed in jail this past Monday. We have a custody agreement although I was already in the process to take custody from her. She is being held without bond for probation violations and a motion to impose guilt has been filed. My child is with her parents right now. She was originally placed on probation for possession of a controlled substances under 1 gram. To recap: would I get in trouble for not bringing my son back to the grandparents Sunday evening as the order states since she is in jail? What do I need to get filed immediately? I'm waiting to see an attorney but that won't be until next week due to scheduling. I want to go for primary custody with her having supervised visitation since my son has seen his mother arrested twice now. He is almost 2.