Rosemary and Laura travel across the country to assist Rosemary's old friend the blind Professor Mullins, who has asked them to look into the odd death of random patches of plants on his allotment.

The duo accompany the professor to an allotment committee meeting to discuss the strange circumstances but are shocked to find that the allotments are to be sold to a building firm.

The professor manages to force a vote on the decision to sell the land and saves the day, much to the disappointment of builder Mr Kelly and site owner Hugo Dainty.

Returning to the allotments the next day, Rosemary and Laura discover the lifeless body of Professor Mullins in a hole near his allotment...