The Devils Forgotten

A pirate galleon in Plymouth Sound? Normal-ish.
A ghost pirate galleon in Plymouth Sound? Not normal.
An invisible ghost pirate galleon in Plymouth Sound? Time for the Plymouth Grey!

The arrival of an invisible ghost pirate ship in Plymouth Sound is the start of another series of paranormal events that must be dealt with by those in the mysterious Grey. Why can only they see it? What brought it to Plymouth? Why is the cemetery guardian worried?
But the events are stranger than even the Grey could imagine as they find their entire existence jeopardised by what has lain hidden underneath Plymouth's Central Park for hundreds of years.