The original idea came to co-author Mary Harrison when she observed her youngest son, Leon, trying to pick flowers from a floral pattern on her bed cover. The infant's actions seemed so quirky and amusing that Mary was prompted to write a letter to Woman's Own magazine which was subsequently published. Mary asked if other mothers had experiences similar "odd" moments with their little ones. The word "odd" was the keyword that triggered an amazing reaction, and Mary, whose address had been published with her letter, was overwhelmed with letters from parents reporting accounts of reincarnation. From this, the idea for the book The Children that Time Forgot was born.

Mary and Peter Harrison spent over a year thoroughly researching leads. The anecdotes and stories developed organically as they gathered new evidence and established facts. Amongst the 30 fascinating accounts they unearthed, one story features a young girl from the north of England, so young she had not travelled outside of England before and was too young to read, yet she recounted, with chilling accuracy, visiting her grandmother in Dundee on the fateful night in 1879 her train was swept away when the Tay Bridge collapsed. Cynics would of course be quick to question the validity of such a story, but when the girl's family recollections were checked out, eyewitness accounts of the family she described, events leading to it, and records matched up.

The book's primary aim is to present children's stories in a neutral, non-judgmental way and let the listener decide. All the stories are spontaneous and all contributors offered their stories voluntarily.