In the sixteenth century, Francis Barnard travels to Spain to clarify the strange circumstances of his sister's death after she had married the son of a cruel Spanish Inquisitor.
An experiment on a simpleton turns him into a genius. When he discovers what has been done to him he struggles with whether or not what was done to him was right.
After a wave of reports of mysterious attacks involving people and pets being eaten by the traditionally docile fruit, a special government task force is set up to investigate the violent fruit and put a stop to their murderous spree.
