Dr Terence Morton, a research botanist, and his wife, Laurie, live in a big house. Their son, William, recently died after eating some powder in his father's laboratory.
Laurie Picks up their newly adopted son, James, from the Nesbit childrens' home. James has some juvenile traits and carries a toy rabbit named Bugsy. Laurie is told by the matron that he will soon grow out of his childish behaviour.
Laurie drives James home. While driving past the churchyard, James comments on what a horrible place it is. Suddenly, Laurie loses control of the car and swerves wildly, desperately trying to regain control as they career down the country lane. James stays utterly calm throughout. Eventually, she gains control of the car and draws it to a halt.
At dinner that night, James and his foster parents sit down to eat a steak. James tells Laurie that he cannot eat his because there are things crawling in it. Laurie looks down and is shocked to see live maggots crawling all over her steak.
Later that night another disturbing event happens. A new cuddly rabbit that Laurie gave James is found with entrails oozing from it. At first, Laurie blames James for the prank, but James is adamant that he had nothing to do with it.
The next morning, James takes Nipper, a rottweiler, for a walk. Laura is absent on some charity work, and Terence is meeting some people from the world food council. His walk takes him to William Morton's grave. While there, a strange earth tremor occurs sending Nipper into a frenzy and he runs off.
Nipper runs into Terence's laboratory and savages all of his experimental rabbits. Terence arrives on the scene with his two visitors and is devastated by the sight. James turns up and again is totally calm.
Later, after Laura has arrived back, and seated at a table with his two guests, Terence's arm is grabbed by Nipper's jaws. Terence is left with no choice but to put Nipper down.
Is William Morton's spirit responsible for the seemingly inexplicable events unfolding in the household?..
That night, James finds a private book written by William Morton. It contains a poem detailing how sad and lonely William felt when he was alive. Laurie is shown this. Then Nipper is heard howling, even though he has been buried. Laurie and Terence arrive in the laboratory where William Morton's vision is seen. William breaks the neck of one of Terence's rabbits, steals one of his prized plant specimens and then disappears outside.
Giving chase, eager to retrieve his plant specimen, Terence falls and dies. William's vision vanishes and James is seen lying by William's graveside. While a wreath grows on William's grave, for all the unloved of the world, James and Laurie walk off arm in arm.