The Ark stays in Kiriath-jearim for 20 years until David moves it to Jerusalem (1-2). This is a slight spoiler since David won't move the Ark until 2 Samuel.
Samuel scolds Israel for worshipping the Canaanite god Baal (a storm god) and goddess Astarte (the sex goddess). Samuel is quite opposed to the Israelites worshipping these gods since they know they're only allowed to worship the God of the Hebrews. Samuel judges these people hard (because he's the last judge) but nothing ever comes of his judgment (3-6).
The Philistines plan to attack the Israelites at Mizpah and everyone becomes afraid. They plead to Samuel for help, so he offers a lamb to God.
The Lord shouts with a voice like thunder and the Philistines became confused. The Israelites take advantage of their befuddlement and slay the Philistines.
Samuel sets up a stone, calling it Ebenezer ("stone of help") as a memorial. The Israelites take back all the towns that the Philistines captured (7-14).
Samuel spends the rest of his time roaming the territories of Israel, judging people for their transgressions against God (15-17), which is not a bad gig if you ask Shmoop.