A what? Isaac wanted to shout. His parents were locked in a what?

It’s too dangerous to give you every clue at once. Protect the information. Discovery would be disaster, for you, and for everyone.

Perhaps we shall see you again.

Your loving father.

P.S. Do not delay. Set the watch in motion as soon as you have read this.

P.P.S. Do not give the watch away during your travels.

P.P.P.S. Do not, for any reason, interact with the past.

Isaac read and reread the letter to try to make sense of it.

His mind flew to dinner table discussions. He’d often rolled his eyes at yet another of his father’s windy lectures on the benefits of Latin or the deeper principles of Greek democracy. He could see his father tamping his pipe before launching into another explanation of Aristotle’s discourses.

Now Isaac would give anything to be lectured to boredom by his father.

He stared at the skull that held the watch.

Time travel.

He’d like to travel, in fact, to another time and place, when he thought about it. It might really be fun. To see ancient Rome or Greece—maybe even sit and listen to Aristotle in the flesh. See woolly mammoths roaming across North America. Witness the building of the Great Wall of China, the Hagia Sophia in Constantinople, or Machu Picchu in the Andes. Why, he could think of a million places he would go with a time-travel device.

Could he even stop the Nazis, make the whole ugly war go away? Be back at home again, with his parents, in Prague, tell them how much he missed them? See his grandfather once more and say goodbye properly?

Except for that admonition from his father: Do not interact with the past.

But then again, all his time travels might be like that nightmare in Orkney and the ring of stones, which he was now certain must have been the first of the four set by his parents. And what should he have found there? What object or clue had he missed, in his ignorance, when he’d foolishly set the watch into motion by accidentally winding the crown?

So, he’d already made one terrible mistake.

Do not delay.

Right, then. No more mistakes. He had to answer this call. For his parents. For himself.

Isaac picked up the watch and turned the crown, setting the timepiece to ticking, closed the face, gripped it tight in his fist so the cold skull dug into his palm, and fell into a whirlwind.

CHAPTER 22

Isaac in the Library of Alexandria

Circa AD 415