Mrs. Petrov is Nancy Drew's neighbor.
Mrs. Petrov's daughter Linda recently married an Englishman named Hugh Penvellyn and moved into his family home, Blackmoor Manor. However, when Mrs. Petrov visits her daughter, Linda acts very strangely and is practically reclusive.
Mrs. Petrov is so alarmed by the drastic change in her daughter's behavior, she asks her neighbor and local sleuth Nancy Drew to investigate. Although Nancy can call her anytime, Mrs. Petrov is babysitting her niece's children and may not be able to always answer.