In Acts 12 persecution of the Jesus followers increases, with King Herod being the one ordering it. First he has the apostle James killed, and then arrests Peter. The believers gather in Mary’s house (the mother of John Mark) to earnestly pray for Peter. Their prayers are answered, but the servant Rhoda is the only one to believe it when first encountering evidence of it, and she doesn’t react in the best way.
While an angel leads Peter out of the prison he thinks it is all just a vision. It is only after the angel leaves him that Peter realizes that he is actually free. He goes to Mary’s house and is left knocking at the gate when Rhoda sees that it is Peter at the gate but she goes to tell the others without letting him inside.