Read Jeremiah 40:1-16
The Babylonian commander, who did not know God, acknowledged that God had given the Babylonians victory. It is strange for people to recognize that God exists and does miracles and yet not personally accept Him. Knowing God is more than knowing about Him. Be sure you know Him personally.
Jeremiah was free to go anywhere. In Babylon he would have great comfort and power. In Judah he would continue to face hardship. In Babylon Jeremiah would have been favored by the Babylonians but hated by the Judean exiles. In Judah he would remain poor and unwanted, but the Judean remnant would know he was not a traitor. Jeremiah returned to Judah.
Mizpah was a few miles north of Jerusalem. Not thoroughly destroyed by the Babylonians, Mizpah served as a refuge after the destruction of Jerusalem.
Gedaliah, appointed governor of Judah, foolishly ignored the warnings of assassination. Ishmael, in the line of David, may have been angry that he had been passed over for leadership. This is similar to the chaotic political situation that Ezra and Nehemiah faced when they returned to rebuild the Temple and the city.