Password to Larkspur Lane

Password to Larkspur Lane, a Nancy Drew mystery by Carolyn Keene, is 175 pages.  Nancy starts off at home.  She and Hannah, her housekeeper, find a homing pigeon carrying a message.  The message is strange because it does not make any sense.  Nancy sees her friend and he tells her a strange story.  When Nancy goes to her car, a man comes up behind her and tells her to give her dad a message.  The message for her dad is 'To mind his own business or he will be in for a bad shock.'  Nancy then goes to see the Cornings because they said something weird was going on at their house.  When Nancy gets there, they tell her there has been a blue ring of fire outside every night for the past couple of days.  Other weird things occur and Nancy thinks that something is going on at another house near the Cornings' house.