It was always going to be difficult escaping from the fortress of Tiryns, and finding a way through the mountains of Arkadia to Ithaka. Hard enough in itself, and harder still when things go badly wrong.

The chase has finally caught up with Odysseus and his friends. They need to find a place to hide, another more devious route to evade their pursuers. What better than a haunted cave, with a tunnel that leads right down to the Underworld? Skotia knows it well – she grew up close by and she knows of a secret exit, far away on the other side of the valley …

The geology of Arcadia is fascinating. In spring, flood waters pour out of the mountains and into a large central plain, but no rivers flow out again. Where does such a vast amount of water go?

This is limestone country, and the water has cut caves through the rock and drilled sink-holes which tunnel many kilometres under the surrounding mountains to discharge their water into the sea far away. One of these caves, on the western side of the plain, is quite famous. It’s called the Kapsia Cave and you can read about it at http://www.herbert-thiess.de/Kapsia/

The cave, or sinkhole, that Skotia leads Odysseus and Eurybates to is about half a kilometre south of Kapsia. It’s called the Palaiochori Cave – a real place but rarely visited and little known. After months of detective work, I found a description of an 1893 exploration, written in French – which I had to translate – along with two detailed maps. The cave map at the start of The Bow is a careful copy of one of them.

It was important for the plot that there was another way out at the far end of the cave. Nowadays there are narrow vertical cracks in the roof that don’t seem to reach the surface. In creating an exit for my book, I took my cue from the Kapsia Cave nearby.

The modern route to the rather spooky caverns at the back of the Kapsia Cave is through a thicket of stalactites. It was obvious to the cave explorers in 1974 that no one had been this way before, because they had to break lots of stalactites to get through. And nowadays there is no other way out from the back of the cave. But somehow there was a pile of bodies in there, people who had entered the cave over two thousand years ago.

Looking around, the modern cavers saw a steep ledge rising up to the roof of the cavern. People had climbed down the ledge, because the stalactites above it were broken off. This must have been the ancient way into the cavern but it no longer connects to the surface. Probably earthquakes – common enough in Greece – had closed an ancient hole.

If it happened in the Kapsia Cave, I reasoned, it could easily happen nearby, in the Palaiochori Cave. Maybe my visit to the cave in June 2014 will give me a few more clues – if I can brave the bats that hide in the narrow crack I have to crawl through!