Characters in The Mystery of the 99 Steps

Nancy Drew

Also in The Secret of the Old Clock, The Hidden Staircase, The Bungalow Mystery, Together with the Hardy Boys, The Mystery at Lilac Inn, The Secret at Shadow Ranch, The Secret of Red Gate Farm, The Clue in the Diary, Nancy Drew, Girl Detective, Nancy's Mysterious Letter

Monsieur Neuf

Bess Marvin

Also in The Secret of Red Gate Farm, The Message in the Hollow Oak, The Haunted Bridge, The Clue of the Tapping Heels, The Mystery of the Brass Bound Trunk, The clue in the jewel box, The Secret in the Old Attic, The Mystery of the Tolling Bell, April Fools Day, The Clue of the Leaning Chimney

George Fayne

Also in The Secret of Red Gate Farm, The Message in the Hollow Oak, The Haunted Bridge, The Clue of the Tapping Heels, The Mystery of the Brass Bound Trunk, The clue in the jewel box, The Secret in the Old Attic, The Mystery of the Tolling Bell, April Fools Day, The Clue of the Leaning Chimney

Carson Drew

Also in The Secret of the Old Clock, The Hidden Staircase, The Mystery at Lilac Inn, The Secret at Shadow Ranch, The Secret of Red Gate Farm, Password to Larkspur Lane, The Message in the Hollow Oak, The Clue of the Tapping Heels, The Mystery of the Brass Bound Trunk, The mystery at the moss-covered mansion