Greek Templar Gold

Acre 1291 The city is besieged by Mamluks and about to fall. Two Knights Templar ships containing a vast amount of treasure and an ornate box containing the Holy Grail manage to escape the siege and sail to Cyprus. But what became of the treasure and ornate box? Seven hundred years later after discovering two gold coins on the seabed off a remote and uninhabited Greek island Adam Evans puts together the cryptic clues that have been left and discovers the long-lost treasure but has he found the Holy Grail?