Paul was probably invited into one of the publicly accessible rooms of the praetorium. Felix came out there to him with Drusilla, who was more interested in Christianity than her husband.
She was a Jewess by birth, the daughter of King Herod Agrippa, who killed the Apostle James and died in Caesarea, chapter 12.
“Paul, though he spoke with a ruler, said nothing that might win over his soul. Rather, he spoke what terrified and shook his heart. Such was the power of Paul’s words that the governor was seized with fear.”
Blessed Theophylact thinks that “Felix knew Paul’s faith well. He knew what pertained to Christ because he had a Jewish wife, from whom he often heard about this.”
Felix himself also could have had comparatively accurate information about Christianity. He had been procurator for quite some time and had lived there even longer; see Acts 23:24; Acts 24:11.
At that time Christianity had already spread throughout all Palestine and Caesarea. But was Cornelius the centurion, converted by Peter, also there at that time?