Sally and Liam Caswell moved from London to a quiet countryside so that Liam, a biological scientist, could work on his book in peace. But he is unable to concentrate and constantly quarrels with his neighbor, old Bodicot. The professor's irritation can be explained by the fact that he is being persecuted by environmentalists. As if to prove this, a package with a bomb arrives at the Caswells' house. The drama of the situation is enhanced by the fact that Bodicot was found dead in the courtyard of his house. Superintendent Alan Markby and his friend Meredith Mitchell understand that there are no coincidences in this tangle of mysteries. Only a thorough investigation will show who is right and who is wrong.