Blue bells will be singing horses! This strange message, attached to the leg of a wounded homing pigeon, involves Nancy Drew in a dangerous mission. Somewhere an elderly woman is being held prisoner in a mansion. Nancy is determined to find and free Mrs Eldridge. While working on the case, the young detective's close friend, Helen Archer, begs her to solve a weird mystery. Helen's grandparents, the Cornings, are frightened by a sinister wheel of blue fire that appears after dark in the woods outside their home at lonely Sylvan Lake. When Nancy discovers the significance of the eerie signal, she also learns that her two mysteries are connected. How the clever young detective fathoms the meaning of the strange message, how she locates the stronghold of a ruthless ring of swindlers and how she rescues the gang's victims makes absorbing and exciting reading.