* Oliver "Ollie" Lamb: A shy and imaginative 12-year-old boy who is obsessed with the mysterious "Elsewhere," a world he believes exists beyond the ordinary. He is the protagonist of the story and the one who embarks on the journey to discover the truth.
* Sarah Lamb: Ollie's older sister, who is initially skeptical of his beliefs about Elsewhere but eventually joins him on his quest. She is more practical and grounded than Ollie, but she is also curious and adventurous.
* The Book of Elsewhere: A mysterious and ancient book that Ollie finds in his attic, filled with fantastical stories and cryptic clues about the existence of Elsewhere. The book is a catalyst for the story, driving Ollie and Sarah's investigation.
* Professor Reginald Blackwood: A eccentric and reclusive author who has written extensively about Elsewhere and other fantastical subjects. He serves as a mentor and guide to Ollie and Sarah, providing them with knowledge and clues.
* The Guardians: A group of mysterious and powerful beings who protect the entrance to Elsewhere and guard its secrets. Their true nature and motives remain ambiguous throughout the story.
Other significant characters include:
* Mrs. Lamb: Ollie and Sarah's mother, who is initially unaware of their quest but later becomes involved in their search for Elsewhere.
* Mr. Lamb: Ollie and Sarah's father, who is more focused on his work and less aware of his children's interests in the fantastical.
These characters all play important roles in the story, shaping the plot and revealing the mysteries surrounding Elsewhere.