When a customer of William Doughty's chemist shop dies of strychnine poisoning after drinking medicine he dispensed, William is blamed, and the family faces ruin. William's daughter, 19-year-old Frances, determines to redeem her ailing father's reputation and save the business. She soon becomes convinced that the death was murder, but unable to convince the police, she turns detective. Armed only with her wits, courage, and determination, and aided by some unconventional new friends, Frances uncovers a startling deception and solves a 10-year-old murder. There will be more deaths and a secret in her own family will be revealed, before the killer is unmasked and Frances finds that her life has changed forever.