Time sphere - a timepathway book

When a teenage priestess, living 5,000 years ago in Ancient Egypt, connects with Rhory, an English schoolboy visiting the British Museum, she puts herself and him in grave danger. The link they forge through the pathways of time is noticed. She must escape the murderous followers of the God Set, and Rhory is hunted by their modern counterparts, the nefarious Society of Secrets.