The Amazing Mr. Blunden

In 1918, war widow Mrs. Allen and her children Lucy, Jamie, and baby Benjamin are reduced to living in a squalid Camden Town flat. A mysterious old man, Mr Frederick Percival Blunden, visits the family, introducing himself as a representative of a firm of solicitors with an offer to become caretakers of a derelict country mansion in the Home Counties named Langley Park. Lucy and Jamie soon encounter the spirits of two other children, Sara Latimer and her younger brother Georgie, who died in the house nearly a hundred years prior. The four children concoct a magic potion that allows them to travel backwards in time to the era of the ghost children.