Mary, mother of John Mark
Mary was the mother of John Mark.
Herod Agrippa had James the Apostle (brother of John the Apostle) executed. Herod Agrippa had Peter the Apostle imprisoned and planned on having him executed as well. The people of the Church prayed to God for Peter, and an angel of the Lord appeared, freed Peter from his chains, and led Peter out of his prison.
The angel left, and Peter went to Mary's house, since there were many praying believers in Christ there. Peter knocked on the door of the house, and the servant Rhoda went to the door. She recognized Peter's voice and was so overcame with joy that she forgot to open the door and went to announce Peter's arrival. The people in the house did not believe Rhoda's claims that Peter was at the door and they argued over it.
Meanwhile, Peter continued to knock. When the people of the house finally open the door, they were amazed to see that Peter was actually there. Peter then recounted how the angel of the Lord helped him out of Herod's prison and told them to report what they've heard to James and his siblings. Peter then left.
When he realized what had happened, he went to the house of Mary the mother of John, who was also called Mark, where many [believers] were gathered together and were praying continually [and had been praying all night]. When he knocked at the door of the gateway, a servant-girl named Rhoda came to answer. Recognizing Peter’s voice, in her joy she failed to open the gate, but ran in and announced that Peter was standing in front of the gateway. They said to her,You are out of your mind!But she kept insisting that it was so. They kept saying,It is his angel!But [meanwhile] Peter continued knocking; and when they opened the door and saw him, they were completely amazed. But motioning to them with his hand to be quiet and listen, he described how the Lord had led him out of the prison. And he said,Report these things to James and the brothers and sisters.Then he left and went to another place.— Acts 12:12–12:17 (AMP)