The ghost novel

The Ghosts is a novel written by Antonia Barber in 1969. It was shortlisted for the Carnegie Medal. It was filmed in 1972 as The Amazing Mr Blunden with Laurence Naismith as Mr Blunden and Diana Dors as Mrs Wickens.
Plot summary
The story opens with an elderly man visiting Mrs. Allen, a widow who lives with her three children Lucy, Jamie and her baby Benjamin, in Camden Town, London, England. He offers her a job as caretaker of an abandoned house of Mr. Latimer until the Blunden, Blunden and Claverton company can find the rightful owner. Mrs. Allen takes the job, despite the rumours of ghosts living in the old house.
One day, Lucy is walking in the garden to explore and to pick flowers when she hears the ghosts calling her name. She goes closer, only to discover the ghosts in person: a teenage girl and her younger brother.Lucy and Jamie return the next day to discuss with the ghosts. It turns out their uncle is trying to "get rid of them", or murder them, and they are travelling forwards in time in order to get help. The ghosts' names are Sara and Georgie Latimer.
By drinking an infusion of various leaves, made from a recipe that Sara provides, Lucy and Jamie go back in time with the ghosts to meet Mrs. Wickens, the housekeeper and mother to Bella who is to marry Sarah and Georgie's guardian.; Tom, the gardener's boy; The children also meet Mr. Blunden (who is believed to be the creator of Blunden, Blunden and Claverton company), who helps Jamie and Lucy rescue Sara and Georgie from a fire supposedly started by their drunk adoptive father.
In the end, Jamie and Mr. Blunden travel through the fire by holding hands, and because Mr.Blunden is the one who must suffer. Jamie will not have to. And they save Georgie while Sara is safely outside. Mr. Blunden dies.In the end, a lawyer named Mr.Smith returns to the household. It turns out Sara married Tom (the gardener boy), and Georgie moved to Camden Town. And Sara moves to the U.S.. According to a letter sent by Sara to Georgie, her great-grandson is the late Mr. Allen, Jamie and Lucy's father, so Jamie is considered heir to the house, being Sara Latimer's great-great-grandson