"The Killers are likely to be children"

May 1968, in a run-down inner city suburb; a little boy goes missing while playing outside his home. His body is found in a derelict house and although he is rushed to hospital, doctors pronounce him dead on arrival. The police hoping for answers from the post mortem on four-year-old Martin Brown find none; the pathologist could find no cause of death.
It would take the death of another child for the police to make the link and come to the conclusion that Martin could have been murdered. The pathologist who examines the body of dead toddler Brian Howe, tells police that the killers are likely to be children.

The police hear from a young boy who saw what had happened to Brian Howe. He tells them what he saw Mary doing. She tells her victim that he has a sore throat and gives it a massage. Then she tightens her grip about his throat and doesn’t let go.
With the violent attacks on her schoolmates, bizarre obsession with questioning the relatives of the dead boys, and her obvious interest in the case, the investigation narrows in on Mary and her friend Norma Bell. Incriminating, semi-confessional notes found at the local Woodlands Crescent nursery, initially dismissed by the police as nonsense were shown to handwriting experts, and are proved to written by both girls. Mary and Norma are brought in in for questioning.