Somewhere, beneath the island of Samos in the eastern Aegean, there was a tunnel, known in antiquity as one of the greatest wonders in the world. Yet the secret of this engineering marvel had been lost for over two thousand years. Until now...

Samos: an ancient city, beautiful, ruled by the tyrant Polycrates, is constantly under threat of Persian invasion. Eupalinos, a young engineer in the 6th century BC, is tasked with constructing a mile-long tunnel under the mountain, designed to bring water to the city in case of siege. Beset by rock falls, political interference and the death of a great many slaves, Eupalinos must complete the tunnel before the city is attacked, but he knows he is running out of time. Digging blind, without the benefit of any modern technical aid whatsoever, he decides to build two tunnels, concurrently, one from each end through the mile-wide mountain, but how will he make them meet ?

When the tyrant Poycrates offends the Gods by his hubris, the fate of Samos is under question. The Persians invade; will Eupalinos survive and will the city - and their tunnels - fall?

In 1853 an elderly archaeologist, Monsieur Victor Guerin, and Eleni, a young Greek woman, set out to look for the whereabouts of the lost tunnel, but over another hundred years must pass before the true wonder of this extraordinary tunnel is discovered.