Once Upon a Crime is the fourth book of the series The Sisters Grimm. It revolves around the detectives Sabrina Grimm and Daphne Grimm. The book is written by Michael Buckley.

Plot

Though Sabrina and Daphne have go their parents back, Henry and Veronica Grimm are still under a sleeping spell and Puck, their fairy friend, is terribly sick after being attacked by a Jabberwocky. Puck is rapidly running out of time so Granny Relda, Mr. Canis, and Mr. Hamstead, and the girls are taking Puck to Faerie, where Puck's family live, where they hope he will be able to help. Sabrina is astonished to discover that Faerie lies is the heart of her old home, New York City. To make matters even more complicated she learns that Puck is the son of the King of Faerie, Oberon himself. Apparently Puck was banished by his father and Oberon is not inclined to help Puck now, even though his son is terribly sick. Finally, his wife Titania persuades Oberon to allow Puck to be healed but soon after the process is begun Oberon is poisoned and dies. It isn’t long before the Grimms find themselves deeply involved in an investigation to find out who murdered Oberon. It appears that Cobweb, a fairy, did the deed. He certainly is on the run and therefore appears guilty of the crime. And yet something about the whole business does not seem quite right. In addition to the investigation Sabrina learns that her mother was not the person she thought she was. Veronica Grimm was very active in the Everafter community in New York City and was much beloved by many of them. Indeed she was trying to find a way to save Faerie. This is very hard for Sabrina to come to terms with at a time when she herself wants nothing to do with the Grimm legacy. She wants to retire from the family business for good and to lead a "normal" life.