A grim but mischievous comedy, this film is based on the true-life story of convicted poisoner, Graham Young. Set in Neasden, London in 1961, Graham has a passion for chemistry. He uses his family and schoolfriends as a control group for testing the toxic content of his concoctions, which leads to illness and death.

Caught and sent to a mental institution for his deeds, he is soon taken under the wing of the institution's psychiatrist, Dr. Zeigier, who believes that the impressionable and intelligent young man can be redeemed. Eventually released and his record expunged, Young soon causes havoc at his new workplace.