While Moses is up on the mountain talking to an increasingly insane God, the Israelites decide that they've been abandoned and decide to create a new, chiller god to worship. Aaron takes all of their golden earrings and, through the skills he apparently had as a gold smith, created a pure gold statue of a calf. The Israelites enjoyed this new God who didn't give them rules or kill them for no reason and decided to have a free for all feast and fuck fest to celebrate.
What happened next? Well, you'll have to give it a listen! But you know how God and Moses feel about fun...
This also closes out the book of Exodus.