Ch 19: When two angels go to remove Lot from Sodom, they are threatened with rape by the men of that city. Lot, unbelievably, nearly gives his own daughters to the men instead, but the angels intervene. Leaving Sodom, the city is destroyed by God, but Lot’s wife by turning back dies. Lot then lives in a cave with his daughters. They get their father drunk and commit incest with him in order to become pregnant. Their sons become the fathers of two great biblical nations that would plague Israel for the rest of time, Moab and Ammon (the present day Amman, Jordan still carries the name).
Ch 20: Abraham again lies about Sarah being his sister rather than his wife in order to protect himself from Abimelech, although his excuse is that she actually is his half sister. Abimelech has a dream from God that he will die if he doesn’t return Sarah to Abraham. He does so, giving Abraham a bunch of livestock in the process. Abraham is called a prophet by God, and upon praying for Abimelech, he is healed (and his wives) of infertility.
Ch 21: Isaac is born when Abraham is 100. Hagar is sent away because Ishmael, Abraham’s first son through the slave woman, is seen mocking (presumably Isaac). In the wilderness, when Hagar and Ishmael are dying of thirst, the angel of God shows them a well at Beersheba. Abimelech’s men and Abraham fight over presumably the same well in Beersheba and a covenant is made that the well belongs to Abraham, but the land beyond is Abimelech’s.