This is the summary of the finale from last season on wikipedia.

>Due to Percival's recent curse, Bailey's Comet is headed straight for Riverdale and a barrier is placed around the town. While no one can leave, people can still enter. Heather and Cheryl summon Abigail on how to destroy the comet. Cheryl plans to use all of her Phoenix powers to destroy the comet, but it will result in one or more of the those who have been resurrected to die. Archie decides to propose to Betty, but she decides to hold off until the comet is destroyed. After watching Titanic, Jughead and Tabitha go on a date with Tabitha using her chronokinetic abilities to see her and Jughead having a family and growing old together. Heather casts a spell to allow Abigail and Toni's ancestor Thomasina to spend one last time together using the bodies of Cheryl and Toni. Mary comforts Archie about his fears of losing his loved ones. Betty decides to propose to Archie, and he happily agrees. Veronica plans to siphon the powers of the gang and give them to Cheryl so she has more than enough power to destroy the comet and keep everyone alive and is successful. The next day, the residents of Riverdale are sent back in time to the year 1955 where the gang are teenagers again and only Jughead remembering the events that happened before.

The show has gone completely bonkers.

After season 1, it turns absolutely insane. If you made up a plot at random, throwing in the most bizarre elements you can think of, chances are it genuinely happened.