The continuing crises of faith of the Israelites.
The people are whining again, this time because they have not water. They complain to Moses, who asks why they're bitching to him and 'tempting' (questioning) the lord. Because the heavenly customer service department only responds to negative feedback? They grumble amongst themselves that they shouldn't have left Egypt, proving for the umpteenth time that gratitude really is the shortest-lived human emotion.
Moses goes to god and says the people are just about ready to stone him. God tells him to take the elders of Israel and his rod to a rock in Horeb where he'll hit the rock with the rod and water will come out. He does, and names the place Massah and Meribah, or temptation and contention.
The next crises is war, specifically with the Amaleks, descendants of Esau. Moses tells Joshua to go fight them while he goes up a hill with his rod. He holds his hands out, and if they drop, the Amaleks prevail, but if he keeps them up, the Israelites do. So he weasels out of fighting, then can't even do his bit by keeping his damned hands in the air. Aaron and Hur have to give him a stone to sit on, then hold his hands up for him, which you would think would be cheating. Joshua wins. God tells him to write a book about this, and promises he's going to wipe out the Amalek people. Another mass killing!
Moses builds and alter, and promises there will be more wars with the Amaleks.
Jethro, or Reuel, as the case may be, whom you may remember is Moses' father-in-law, comes, along with Moses' wife and two sons. We know that Moses sent them back, but not why. Moses greets Jethro, though there is no mention of his reaction to seeing his spouse and kids, despite the fact that she saved his life a few chapters ago. Moses tells him everything that has happened, and Jethro praises the lord and says he's the greatest god ever, and makes a sacrifices to him and they all eat.
In the morning, Moses sits down outside and the people come to him to ask him to judge their disputes. Jethro asks what he's doing, and Moses explains that he makes his judgements bases on what god's laws and statutes say. Jethro, like many a meddling in-law, says he's not doing the right thing. This guy who just converted last night. He says he's wearing himself thin, and needs some helpers. He suggests training some assistants in god's rules, and finding some god-fearing, honest, uncorruptable men to act as officials. Moses himself will only handle the biggest issues, but they'll do the everyday stuff. Basically, he's setting up a judicial system of local, appellate and superior courts here. Moses takes this sensible advice and appoints various magistrates. Jethro goes home.