This takes place 2 years after Forever. Cole travels to CA to get Isabel and bring her back to Mercy Falls. But things have changed from what Isabel remembers and she has to choose whether or not she wants to live with the changes and Cole or whether she should go back CA on her own. *No spoilers for Sinner [I still haven't read it ;)]*

The team goes to a high school to investigate a chemistry experiment that went horribly wrong. While there, they encounter a student named Kota, who might also be a genius. Walter rushes to recruit her on the team before her family ruins her chances of ever being successful.