The O’Brien Detective Agency Series

  • Published by Scholastic Canada, 1991 – 1996, for Grades 3-5.

Elementary school student, Clarice O’Brien is the Chief Detective at the O’Brien Detective Agency and, along with her best friends Sadie and Brick, she always manages to get to the bottom of the neighborhood’s mysteries.


“Our Choice”, Canadian Children’s Book Centre, 1991 and nominated for the Manitoba Young Reader’s Choice Award. Miss Parsnip has asked the O’Brien Detective Agency to find her missing cat, and Clarice O’Brien is eager to take the case. But it looks like the case of the marmalade cat isn’t the only mystery around. Clarice’s best friend Sadie thinks Miss Parsnip looks and acts an awful lot like a witch… and their new friend, Brick, can walk on fences, climb on roofs, and talk in cat language!


Someone is stealing toys, and the O’Brien Detective Agency is on the case! A trail of clues leads Clarice, Sadie and Brick all over the neighbourhood, without bringing them one step closer to the clever thief. They are running out of time… but maybe, just maybe, this thief’s cleverness will give him – her? – away!


The O’Brien Detective Agency is on holiday in Greece.But when a mystery falls into their laps, they can’t resist. The gold ring of the Minotaur has been stolen, and all the clues point to one of the Canadian kids staying at their hotel. Can the detectives find the thief—and the magical ring—before it’s too late?


“Our Choice”, Canadian Children’s Book Centre, 1997-98. Shortlist, Arthur Ellis Crime Fiction Award, 1997. On the trail of a roving rabbit, the O’Brien Detective Agency bumps into a new mystery: a raccoon that keeps showing up where it shouldn’t. Soon Chief Detective Clarice O’Brien is pitting her wits against a crooked pest control man. Brick and Sadie are right behind her – but Sadie can’t stop thinking about the missing bunny. Are the two cases related? Could the mysterious musician be the link between them?


THE CASE OF THE MARMALADE CAT. REVIEW BY JAMES, GRADE 4, MR. PRICE’S CLASS, MIDDLEBURY PUBLIC SCHOOL, ONTARIO. The Case of the Marmalade Cat starts off with Clarice, a girl who likes detectives and wants to be one to. Clarice told her friend Sadie and then she wants to be in the agency too. On their second day in business a boy named Brick wants to join and he convinced them that he would be a good detective and so then he became the third and final detective in the agency. Now they only needed to get a case. Then it happened in the mail-box was a letter. They were to find a missing cat for Miss Parsnip. Strange things go on during the case. Sadie thinks Miss Parsnip is a witch. Brick can walk on fences and talk in cat language. This book takes you too many different places and strange ones too. I didn’t really like that I could guess what was going to happen before it happened. If you like mysteries this is a good book to read.

THE TRAIL OF THE CHOCOLATE THIEF. REVIEW BY CAROL, A STUDENT AT WILLIAMS BRIDGE ELEMENTARY IN RICHMOND, BC PUBLISHED ON THE BC LIBRARY ASSOCATION WEB SITE. Clarice O’Brien is the chief detective. She and her friends Sadie Stewart and Brick (Leopold) Chumley-Smith are on the trail of a Robin Hood chocolate lover thief. Lots of kids lost their toys and all the kids live on False Creek but only one lives in Fairview…I liked the part when Clarice always say, “That is my hunch.” I also like it when Clarice is impressed with the detectives, she sounds so serious.

THE TRAIL OF THE CHOCOLATE THIEF. REVIEW BY DAVE JENKINSON IN CM MAGAZINE (May/June 1994, Grades 3-5, Ages 8-10). …While The Trail of the Chocolate Thief can stand alone, readers familiar with The Case of the Mamalade Cat, might better understand the relationships among the characters, especially Number Two’s sarcastic comments directed at the Chief, and will more fully appreciate the children’s run-in with Dolly Varden and her cat Ginger. A good, readable introduction to more sophisticated juvenile mysteries.

THE MYSTERY OF THE GOLD RING. REVIEW BY IAN MCLAREN IN CM MAGAZINE (September 15, 1995, Grades 4-7, Ages 8 – 11.) …In this episode, the three sleuths (all around twelve or thirteen years of age) are on holiday in Greece with Sadie’s parents. During their stay, a priceless ring is stolen from a local museum. The evidence seems to point to one of the kids from a Canadian school band who are also staying at the hotel. …Heneghan makes no bones about this being a Canadian story. Many references are made to sites in the Vancouver area (where Heneghan lives) and the main reason the children want to solve this case is to preserve the honour of Canadians everywhere. If you want your kids to read Canadian content, look no further. Heneghan also manages to weave a fair amount of Greek history, geography, and mythology into this novel… Without realizing it, the reader could end up learning something. The Mystery of the Gold Ring is a very readable, well-narrated pre-teen mystery. Copyright © 1998 the Manitoba Library Association.