Here’s what we know so far:

* Jason had some kind of relationship with Betty’s sister Polly, which ended in a messy way. Polly ended up in a group home, apparently having had some sort of a breakdown.

* Jason wanted to leave Riverdale forever, in a way that would ensure his parents would never find him. So his twin sister Cheryl helped him stage his own death at Sweetwater River on July 4. They said goodbye on the Greendale side of the river, and Cheryl expected to hear from Jason within a month.

* Jason was killed around July 11. He’d been tied up, tortured, shot in the head and, at some point, frozen. His body somehow ended up back at Sweetwater River months later.

* Archie and Miss Grundy were at Sweetwater River at dawn on July 4, as were Dilton Doiley and his scout group. Doiley shot a gun that morning, which Archie, Grundy, Cheryl, and Jason all heard. Doiley later found Cheryl after she had staged Jason’s drowning.