Aunt Estelle, Bess, George, and Nancy travel to Italy and find a mystery to solve, while Joe and Frank also go to Rome and get involved in a mystery concerning the ancient ruins.
When Nancy goes on vacation in New Orleans, she and the Hardy boys investigate a crooked real estate scheme and the appearance of a dead body at a masquerade party.
While helping a friend locate her missing father, a scientist at Tercon Industries, Nancy Drew teams up with the Hardy Boys who are investigating a faulty product manufactured by the same company.