He didn’t wait for Jan. He didn’t stop, even when he heard the shouts. He ran and ran and ran.

*   *   *

A Totenkopf. Isaac’s shame from the memory of running away.

This skull in the casket. Memento mori. Isaac remembered the full Latin translation. Remember that you will die.

There must have been a reason his parents gave him this object, and Isaac was certain it wasn’t to scare him. Steeling himself, sweating a little, he reached inside and lifted the skull out of the casket.

It was as icy cold as he remembered. As he lifted it out, the skull moved as if alive and he dropped it back into the satiny fabric out of shock. Then he leaned over again.

The skull was hinged at the jaw, and the jaw had fallen open.

Isaac leaned closer. Ornate and tiny but detailed carvings covered the skull. Flowers and birds. A man and woman in a garden. An image of Death with a sickle, standing before a hut to its right and a castle to its left.

If it hadn’t been carved on a skull, Isaac would have thought it beautiful.

With one finger he pried the jaw all the way open, and inside, enclosed within the skull, was a watch.

The clockface was fixed on the jaw’s underside with the movement beneath, all the tiny gears just visible. The hands, shining gold, were set at eleven o’clock. The crown at the top of the watch was filigreed. Isaac leaned closer still. The crown was in the shape of the eternity knot. Carefully, he lifted the skull with the watch out of the casket and set it on the floor, the jaw open.

Then he saw that a piece of parchment lay at the bottom of the casket.

A note?

It crinkled in his fingers. Dear Isaac.

The handwriting—there was no mistaking it—was his father’s. Isaac took a breath and rubbed his eyes hard.

I cannot put this gently. You must not delay. You are, as we were in our last days in Prague, being hunted. By something that has been searching for us for a very long time. And I do not mean the Nazis.

Isaac glanced at the window, at the swirling mist outside, the gray light.

We must give you these lessons from afar because that will help throw off your pursuers for a little while. This watch is a time-travel device.

A what?

Wind the crown to set it in motion. We’ve set the first four travels for you. In each time and place, you must seek the next piece of information. Find the object or clue we have left for you. Be absolutely certain you hold the watch firmly in your hand when it chimes at the end of each travel.

Your mother and I can’t help except in this way. We are now—in all probability—locked in a time-stream.