When Heather unveils her new Chocolate Chip Custard Donut, she expects a large crowd, but she didn't expect it to include the angry private investigator Inspector Lemon who accuses them of stealing his cases and then leaves them on a threatening sour note. But after Inspector Lemon is in a suspicious car crash, Heather and Amy are all set to find the culprit who sabotaged the car. Matters become complicated when Lemon's last words seem to implicate Amy in the crime. Follow Heather as she has to sift through the investigator's cases so she can clear her bestie's name and track down the real killer.