So one day, right when everyone least expected it, Sarah gave birth to a son. She was pretty happy about it, and so was Abraham. God finally got around to doing what he'd been promising for a long time. Or he lost a bet.
They named the child Isaac, and circumcised him just like they were told, and when he was weaned they had a party. Don't know if there were pony rides. Probably.
Sarah got a little antsy about Ishmael and "that slave woman" being around, and told Abraham to get rid of them both. So write Sarah's name down in the 'asshole' column. Abraham was pretty torn up about it, Ishmael was his son after all, and judging from the former story of Sarah actually BEING his sister, I'm guessing Ishmael got a better mix of genes. But god told Abraham not to worry about it. Being lost in the desert, that kind of thing builds character, makes a man out of you. Go ahead and send them away, I'll take care of things. Abraham did what god said. He loaded Hagar down with provisions and sent them both on their merry way.
Well, they ran out of food. Then they ran out of water. Turns out the latter is pretty important to have in the desert. Hagar laid her son down under the shade of a bush and went and sat by herself so she didn't have to see him die. She started to cry.
God asked Hagar why she was crying. . . God always asks Hagar stupid questions. She's good, though. She never replies, "Hello? Omniscence? Why must I spell it out for you? Are you drunk again?" God told her to get her son up from under the bush, because Ishmael was going to be a great nation. A nation of very, very thirsty people. Ah! Lo, and behold, she suddenly saw a well. Of water. It's maaaaaaagic.
Ishmael grew up and became an archer, and his mother got him a wife from Egypt.
Meanwhile, back at the ranch:
Abimelech (remember him?) and Abraham were working on a mighty good little treaty, the one where they each swear allegianc to the other, and there might be some spitting into handshakes and secret decoder rings. And Abraham mentions this water well that he says Abimelech's servants had taken over. And Abraham gives Abimelech some ewes to make sure he knows that the well really did belong to Abraham. And after that he goes home and plants a tree near it. And stays there for a long, long time.