Its 1917. A black wreath is put on the front door of a terraced house. Soon after, a mother with 2 children and a baby are seen moving out of the house.Its now a dark early Christmas evening and a smartly dressed old man is weaving his way through the market in Camden Town, noticeably shying away from a lit brazier. He knocks on the door of a dingy basement flat to which this family has now moved. He quickly explains he is not a rent collector but a partner in a firm of solicitors Blunden, Blunden, Claverton and a 4th member he cannot remember, who are seeking a reliable person to act as caretaker to a property in the firms charge. He is reluctant to go into details other than its a bit remote, but there is a rent-free caretakers cottage and the duties would be light. Saddled with little money other than a widow's pension and large debts, the mother (Mrs Allen) is tempted. The old man asks the 2 children Lucy (Lynn Frederick) and James (Garry Miller) if they would be afraid if they saw ghosts - say of children their age or an old man such as himself. He warns them they will hear tales about the house but when the time comes, they will know what to do.When the family accept his proposal, he visibly brightens and outside disappears mysteriously, saying to Lucy and James "We 3 Kings of Orient are my dears".Next day the family present themselves at the solicitors address. The clerk is puzzled as the job had not yet been advertised but shows Mrs Allen in to the partner Mr Claverton. Whilst waiting for their mother, Lucy and Tom see a picture of their visitor - Mr Blunden. The clerk retorts that is a picture of the current Mr Blunden's great grandfather who died 100 years ago and doubted if they had seen even the current Mr Blunden who was bedridden and senile.Mr Claverton delightedly offers the post to Mrs Allen and soon the family is travelling by bus to Langley Park, Buckinghamshire. The house proves to be derelict and overgrown and the cottage very sparse. They go to bed that night wondering what they have done.Next morning Lucy explores the house which has been extensively damaged. She hears childrens voices upstairs but is then startled by the presence of Elsie Tucker the daily cleaner. She mysteriously tells Lucy that the voices she hears are only kiddies.The following day the sun is shining and Lucy is happily picking flowers when out of a sudden mist she sees two figures approaching. She initially flees to find James but both return in time for the approach of two children dressed in old clothes. The ghost children, called Sara and Georgie, are pleased that Lucy and James have not run away and Sara recounts their story. Their parents had tragically died in a carriage accident in 1818. Their father's half brother Uncle Bertie, who lived in London, became their guardian as had the family solicitor Mr Blunden. Uncle Bertie, despite appearances, was short of money and often returned to Langley Park to steal and pawn the family silver. He subsequently married Bella, a simple chorus girl, and with her parents moved into Langley Park. He admitted to his new mother-in-law Mrs Wickens (Diana Dors) that he was hopelessly embarrassed financially. He explained that 10 year old Master Georgie was the only member of his family with money - £30,000 which was held in trust for him until he was 21. Uncle Bertie and Bella would only inherit this money if Georgie died before then.Appalled at this revelation, Mrs Wickens assumed the role of housekeeper and sacked most of the staff at Langley Park as part of an economy drive. Mrs Wickens then got the idea that if the children caught their death of cold, her Bella would be in the money. She fed Sara and Georgie only on scraps and ordered the remaining servant - the timid Meakins - to make sure when she took their food up to their room that their window was left open during the cold nights. However Tom the gardeners son was very fond of Sara and used to climb up the drainpipe to their bedroom to provide them with newspaper to go under their bedding to help keep them warm and then close the window on his way downSome months passed until one night Sara and Georgie overheard the frustrated Mrs Wickens saying it was taking too long and a quick accident was now required. Sara burst in on Uncle Bertie to tell him and also wrote to Mr Blunden explaining their plight but neither believed her and ordered Mrs Wickens to prevent them running away at all costs by locking their window and bedroom door.That following night Georgie saw a message appearing on the window which said "look in library". Meakin had forgotten to lock the door so they crept down to the dusty old library. They saw an arrow drawn in the dust pointing to a book which contained a single sheet headed "A charm to move the wheel of time". It contained a recipe for which they had found the necessary herbs in the garden to concoct a potion, trying it first on the unsuspecting Mrs Wickens to make sure it wasn't poisonous. They used the potion to travel forward in time to try and get help and now Lucy and James are the first to stay and listen to their story. Their own potion is wearing off but before they leave Sara begs Lucy and James for their help and gives them the recipe for making it so they could travel back with her in future.The next day the children are in church when James gets Lucy to leave with him early to search the graveyard. Lucy refuses to help but James finds a grave for Sara and George Latimer dated April 21st 1818 ie 100 years ago tomorrow. They are startled by the sexton who says he's been there 40 years and knows the stories of each grave. He says a fire started in the library while the children lay in their beds and nobody could get to them to save them. He showed them another unmarked grave which his grandfather had told him belonged to the gardener's son, trying to save them by climbing up the drainpipe but he had fallen to his death.He said one of the guardians had left for London but his carriage had broken down. When he saw the flames he rode back to no avail saying over and over again that he was too late and subsequently died of a broken heart.Lucy and James now brew up the potion and meet Sara in the garden who says Georgie has been locked in the cellar. She begs them to return with her. Mr Blunden also appears and says he has a chance to put things right, promising them he will guard them and no harm will come to them.Lucy and James take the potion and travel back to 1818. They meet Tom who excitedly reckons they have come from America - the new world - where one day he hopes to go. They quickly realise no adults can see them, the exception being Bella who has the mind of a child. They spook her into getting her mother to release Georgie from the cellar.That night the 4 children eavesdrop on a dinner involving the Mr and Mrs Wickens, Uncle Bertie and Bella and Mr Blunden. As Mr Blunden leaves with Uncle Bertie, Sara and Georgie rush down to beg them to stay. The children are carted off by Mrs Wickens and the ghost of Mr Blunden appears to James, telling him to wait until the time comes. Then the ghost Mr Blunden goes down the stairs to be subsumed into the body of the living Mr Blunden.Lucy and James realise the nursery where Sara and Georgie sleep is above the library where the fire will start. They try unsuccessfully to get the keys off Mrs Wickens and rush outside to see Mr Wickens carrying a bundle of wood to the fire he has just started outside the library. Lucy waits for Tom who climbs the drainpipe to rescue Sara and Georgie, while James goes for an axe to break down the locked bedroom door. Mr Wickens sees Tom and tries to pull down the drainpipe but Lucy sufficiently distracts Mr Wickens to enable James to smash down the bedroom door and then smash the window locks to enable Tom to clamber in to safety. They find Sara and Georgie have been drugged but James leads Sara first and then Tom outside to Lucy and safety.James is afraid to go back in to the inferno to rescue Georgie but Mr Blunden appears back on horseback and promises they will go in together and he will protect James. They find Georgie and Mr Blunden pushes James and Georgie to safety before succumbing to the fire saying "Thank you Thank you". Georgie stumbles out of the house but theres no sign of James, leaving Lucy screaming for him and crying "You're always too late Mr Blunden".Her potion now wears off and shes back in the garden in her own time. She eventually finds an unconscious James lying outside the house and he is taken to his room.Next day being Sunday and with James still unconscious in bed, Lucy is in church when she suddenly decides to search the graveyard. This time there is only a gravestone for Mr Blunden with the inscription "He gave his life to save the children in his care" and dated April 21st 1818.As she wanders back home, her mother calls out that James is awake. Lucy tells James what she saw and they laugh with relief that the rescue had been successful.Sometime later a car pulls up and Clutterbuck gets out for a private meeting with their mother. Lucy and James gloomily say goodbye to the house and garden when their mother calls them. Clutterbuck says that Mr Blunden had suddenly got out of his sick bed the previous Thursday and ordered him to find the papers on the marriage of Miss Sara and Master Tom who are now revealed to be great-grandparents of their father. Sara Latimer had married a Tom Mortimer and they had sailed to America. As direct descendants, this makes James and Lucy legal owners of the house and cottage with an annual allowance of £500 for the rest of their lives.Clutterbuck leads them back to the car where he says all will be revealed. Inside is Mr Blunden and in reply to the childrens' question "which one are you?" says "We 3 Kings of Orient are" and gives them a wink.In front of their bemused mother, Lucy and James rush delightedly round the garden before the cast give their farewells.
Output: Question: Who discovers that the children's gravestone has been replaced by another?, Answer: Lucy