Incarcerated but free

Background:

Acts 12:3

Up to this point Herod is the king and because he is Jewish he is trying to appease the Jews that he might to continue to find favor with them. So he takes James who is a Christian and executes him.  Now this really pleases the Jews and Herod went further to seize Peter 1 because he was the leader of the church and 2 he was fraternizing with the Gentiles. Herod now sees the opportunity to really please the Jews

 And because he saw that it pleased the Jews, he proceeded further to seize Peter also.

so now Herod has Peter arrested him, he put him in prison, with four squads of soldiers to keep him, from escaping as Peter had already escaped prison twice before.