Acts 12:12

‘And when he had considered the thing, he came to the house of Mary the mother of John whose surname was Mark, where many were gathered together and were praying.'

And once he had thought everything through (as far as he could) he sought out the house of the mother of John (Yohen - Hebrew) Mark (Markos - Greek), where he knew that Christians would be gathered and waiting anxiously to hear news of him, and where indeed many were gathered and were praying.

John Mark was the man who would shortly accompany Paul and Barnabas on their first missionary journey (Acts 13:5). He was Barnabas' cousin (Colossians 4:10) who would later travel with Barnabas to Cyprus when Paul chose Silas as his companion for his second missionary journey (Acts 15:37) after a disagreement over Mark. Mark later accompanied Paul again (Colossians 4:10; Philemon 1:24) as well as Peter (1 Peter 5:13). According to early church tradition he wrote the Gospel that bears his name, served as Peter's ‘interpreter' in Rome, thus obtaining much of his information from Peter, and later established the church in Alexandria, in Egypt