The Case that Time Forgot: The Sherlock Files #3 (Unabridged‪)‬

Xander’s classmate gives a report at school about a famous amulet of the Egyptian god of time, Thoth. It was thought to be so powerful that it could turn back time one day every hundred years. And that day will come in a week!
The amulet disappeared from a museum in London years ago. Xena and Xander’s celebrated ancestor, Sherlock Holmes, tried to find it, but with no luck. The twins are on the case—but so are some mysterious foes who are trying to thwart and perhaps even harm them! Can Xander and Xena track down what Sherlock Holmes could not?