Separated with verbal custody agreement help needed

My wife and I are separated since April. She left me and our adopted son. We have agreed to weekly joint custody. We meet every Sunday to drop him off. I am scared my wife is going to take our son this Sunday and never return him to me or let me see him again. Can she legally take him and not return him to me. I live in our old home with our son. Please help me !!

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If there is no visitation order in effect then either parent has the legal right to take the child at any time. You can see how this would end up treating the child like a ping-pong ball.
If your spouse takes your son and refuses to return him, then you need to get yourself down to the courthouse and file for divorce, and request temporary custody of your son until the date of the trial.