The gaze in the shadow

November 1502. In Raphael's own city, the Duke of Urbino has fled in the night.

The city is untouched and belongs to no one. The shops open. The great building works stand still with their scaffolding up, and cut stone waits under the snow for a wall no one has ordered raised.

Far from Urbino, on the same November night, four strangers each receive a pigeon carrying the same mark. Six strokes, drawn without lifting the pen, in no language on earth. None of them can reply - a pigeon flies one way only.

A water-diviner who feels a hollow behind the stone and cannot prove it.
A woman who measures, and proves the hollow cannot be there.
A bell-ringer who knows a flaw inside bronze by the way the sound comes back.
A boy on the rooftops who sees a city no one sees from below.

They are all right. That is the problem.

Through one winter beneath a palace that has changed hands and not yet changed masters, four people who cannot show each other what they know follow marks cut into working stone by men dead a thousand years - and by someone still alive.

No magic. No prophecy. No one was chosen.

And there is a second book inside this one.

Read it alone, as a novel. Then read it again with three others - each of you taking only your own character's chapters, and applying what you learned to the thirty-nine marks printed at the back.

Four methods. Four different answers. No solution is printed anywhere in the book.

This book can be read again by four. Then it says something else.