Mysterious old solicitor Mr. Blunden visits Mrs. Allen and her young children in their squalid, tiny Camden Town flat and makes her an offer she cannot refuse. The family become the housekeepers to a derelict country mansion in the charge of the solicitors. One day the children meet the spirits of two other children who died in the mansion nearly a hundred years prior. The children prepare a magic potion that allows them to travel backwards in time to the era of the ghost children. Will the children be able to help their new friends and what will happen to them if they do?

This children's fantasy tells the story of a 12-year-old boy who discovers a complex underwater world where young children are held prisoner by an evil shark and an eel.

一个风雪的夜晚，父亲被抓走，鲍比—家的安宁被这突如其来的打击破坏了。母亲带着三个孩子离开伦敦，来到约克夏郡的乡下。母亲整日为家里的生活操劳，鲍比、菲力斯和彼得三个孩子整日在铁道旁玩耍。母亲不幸病倒，三个孩子向一个过路的老绅士求助。老绅士帮他们治好了母亲的病，安排好他们的生活。三个孩子非常感谢这位善良的老人，他们在铁道上做了很多的好事，包括救了一列火车，抢救摔断腿的男孩，后来得知，这个男孩就是老绅士的孙子。老绅士帮忙奔走，孩子们的父亲获得保释，全家团圆。