Currently, students are reading the following core mystery novels in groups. Once they finish their novel, they choose the next mystery novel that they will read, in order to prepare themselves for their Missing Persons Assignment.
Core Books

The Westing Game, by Ellen Raskin
Card catalog description:
"The mysterious death of an eccentric millionaire brings together an unlikely assortment of heirs who must uncover the circumstances of his death before they can claim their inheritance."
Ms. Cognato's Westing Game Website

From the Mixed-up Files of Mrs. Basil E. Frankweiler, by E.L. Konigsburg
Amazon.com Review:
"After reading this book, I guarantee that you will never visit the Metropolitan Museum of Art (or any wonderful, old cavern of a museum) without sneaking into the bathrooms to look for Claudia and her brother Jamie. They're standing on the toilets, still, hiding until the museum closes and their adventure begins. Such is the impact of timeless novels . . . they never leave us. E. L. Konigsburg won the 1967 Newbery Medal for this tale of how Claudia and her brother run away to the museum in order to teach their parents a lesson. Little do they know that mystery awaits!"

Murder on the Orient Express by Agatha Christie
From 500 Great Books by Women; review by Vickie Sears:
"Murder on the Orient Express is a tour-de-force variation on the theme of the English house-party, gathering a remarkable set of characters, each a secretive soul, for a journey on the fabled Orient Express train as it travels from Istanbul to Paris. On hand to resolve the murder of an American passenger is Hercule Poirot, the dapper Belgian detective, dependent only on his wit, who tucks away obscure, seemingly unrelated minutiae in his facile mind. When he determines that the corpse was a renowned child kidnapper/killer, he begins to wonder about connections between the passengers and the victim. A misplaced button, overheard conversations, a monogrammed handkerchief, and an elusive figure clad in a scarlet kimono all become clues as Hercule Poirot interrogates the snow-trapped travelers and comes to his own conclusions. Murder on the Orient Express, with its skill plot construction, adroit writing, and thought-provoking revelations, reminds us that what is "just" is not always what is legal."