Russian Language Five young detectives and a detective dog. Book 4. The mystery of anonymous letters
 
The young detectives and the detective dog are together again and are ready to investigate the most mysterious cases. But alas, everything is calm in Peterswood and nothing unusual is happening, except for the unexpected departure of Gladys, the maid of Pip and Betsy. The guys are sure that everything is not as simple as adults say, and they are right. Residents of Peterswood, one after another, began to receive unpleasant anonymous messages. Who is the author of these mysterious letters? Five young detectives and a dog-detective will reveal this secret!