Unlike the children's song, "Old McDonald Had a Farm," old O'Reilly's farm has more than cows and chicks to worry about. The Mystery at the O'Reilly Farm begins when an elderly farmer decides to sell his Florida acreage when he can't find good help. He asks Micky's dad, a real estate agent, to sell it. While poking around at the farm, 8-year-old Micky and his friends discover jewelry hidden in a bird's nest. Who in the world put it there? And why? Dig out your Sherlock Holmes magnifying glass so you can help Micky figure out this puzzling mystery.