The son of my ex-husband's wife harms my son while visiting father. What to do?

Hi

My ex-husband got married. His wife has a kid from a previous marriage who stays with them, and my kid goes on weekends to stay with him as per court order.

My question is in case my child faces any abuse or attack from his wife and kid, what can I do?

Can I file a police case or file a case in court?

Can I stop his father from taking my child to his apartment?

My child is 10. Please advise.