Dawn Griffin tries to make do with clerking in a fabric shop and fills her idle hours solving daily crossword puzzles. A strange picture postcard from her landlord sends her searching the arts for explanations of the ancient mystery of Medusa.

Soon unsatisfied with musty tomes Dawn questions the circumstances around a local murder and immerses herself in harmless sleuthing. She is aided by the flamboyant lover of her gay landlord and discovers a transvestite whom she later is suspected of killing. Her penchant for puzzle solving uncovers a layer of crimes heretofore unconnected by local law enforcement. Hours spent in the fabric shop arranging merchandise reveals the missing link - and identifies the killer.

Her relentless search links separate investigations and solves them all. In a final attempt to reconcile with her estranged lover she confronts the investigating policewoman with the evidence and endangers them both. She struggles valiantly to save her lover and wins the apology of other law enforcement officers. But her overwhelming personal pride comes from solving the original mystery of Medusa's grin.