David and Jonathan chat while chilling on a rock. Image from LookandLearn.org
King Saul, who still does not know that Yahweh (aka God) doesn't want him to be king anymore, is still squabbling with the young David, who seems to have attracted Yahweh's favor.
In this chapter, Saul reveals some of his nefarious plans to his son Jonathan. But, as we read in the last chapter, Jonathan seems to have, at the very least, a mancrush on David. It may even be more, but I won't go there. He listens to his father's plans, and then defends David, even to the point of making the king swear that he won't kill David because David never did anything against him personally.
This suffices for a while, until war breaks out with the Philistines again and David annihilates them, which just makes Saul look bad again. Saul is becoming such a dark figure that he's actually portrayed sitting down with a javelin in his hand; possessed by "the evil spirit from the Lord." He actually tries to kill David himself, but David escapes and a pissed off Saul throws the javelin at a wall.
Saul is really starting to get jealous now, and decides to send assassins. The Bible calls them "messengers", but they were specifically sent to observe David and then kill him. So, I think "assassins" is a better word here. Though, to be exact these were unusually polite assassins. They actually went to the door of the house and said something to the effect, "Hi, may I see David so we can slay him?"
The people of the house helped David escape, and the assassins were perplexed that David's friends helped him escape. Well, this hit was getting a little tricky for the friendly assassins.
David escaped to Samuel, whom the book is named after. Samuel, if you've been following me, is a prophet. When the assassins saw the prophets prophesying as if they were appointing David, the assassins also realized the err of their ways and also began prophesying, returning to Saul and telling him what transpired.
Two more times Saul sends "messengers" and each time they return prophesying. All this prophesying seems to get Saul all worked up, because he then takes off all his clothes and lays down all day and night, and prophesies himself. The chapter ends here, but I smell a resolution to the power struggle coming soon.