Spoilers for the Riverdale Season 2 finale ahead.
After the momentous cliffhanger that ended Riverdale Season 1, the show had to make some big moves to ensure that the Riverdale Season 2 ending was just as suspenseful. And so, just as the the town is starting to settle into a Riverdale safe from the Black Hood, Archie Andrews is arrested for murder. In the final moments of the episode, he's pulled away from a town-wide celebration by police. Archie didn't kill Cassidy on Riverdale; in fact, it's likely that Archie himself isn't sure who the police are talking about. And fans may not remember the victim either.
To say a lot has happened in Season 2 of Riverdale would be an understatement. With both Black Hoods, the mayoral elections, the spread of Jingle Jangle, Southside Serpent drama, Cheryl finding out that her dad has a twin brother who then sends her to conversion therapy, the break up of the Pussycats, and the whole Chic Cooper mess going on, it's easy to forget that the core four characters of Riverdale managed to find time to go on a forest getaway. Their trip to the Lodge family cabin — or as Veronica calls it, the "Lodge Lodge" — takes place in the episode "Chapter Twenty-Seven: The Hills Have Eyes," and marks the first and last appearance of the boy whose death could be sending Archie to prison.
Cassidy (Harrison MacDonald) is introduced as a happy-go-lucky store clerk at a general store near the Lodge Lodge. While purchasing some incidentals, Veronica playfully flirts with the cashier, much to Betty's annoyance. They talk for a bit about how much Veronica enjoys being back in nature and the quality of her parent's cabin. She asks for the cashier's name and he answers, "I'm Cassidy." This is the only time the character's name is said until Archie is arrested for his murder eight episodes later.
Later in the episode, Cassidy dons a black mask and collects a group of like-minded criminals to rob the Lodge Lodge. The young men, clearly in over their heads, don't expect Veronica to trigger a silent alarm while they're ransacking the Lodge and when they discover they've been found out, go running. However, before leaving, Cassidy snatched Veronica's necklace. Archie chases Cassidy through the woods to try and get the necklace back, tackling him to the ground and removing his mask. Andre —Hiram's assistant — stumbles upon the scene and asks Archie to leave. As Archie leaves the forest, a gunshot rings out. Andre has shot Cassidy.
While other criminals might see an unnecessary death as an inconvenience, it seems that Hiram Lodge saw Cassidy's death as a tool he could use. It's heavily implied that Hiram is responsible for framing Archie, and with Andre dead at the hands of Papa Poutine's son, there is no living witness to Cassidy's death aside from Archie. While Archie could likely convince his friends that he is innocent, he'll have a lot of trouble going up against Hiram's expensive attorneys — especially when Archie has quite a reputation for being violent. It's safe to say that that "Red Circle" video of him threatening to hunt down a serial killer probably won't look good in court.
While this death seemed inconsequential to their lives at the time, Cassidy's demise has just made things a lot more difficult not just for Archie, but also possibly for Hiram. Will Archie still be able to serve as class president when he's on trial for murder? Won't putting Archie on trial give him the opportunity to testify, under oath, about Hiram's criminal dealings? Why is the most powerful criminal syndicate in Riverdale concerned with framing a teenager for a murder that no one in town even cares about? There are a lot of loose ends to be tied up, leaving fans looking forward to Season 3 already.