Treasure is Where You Find It

The three children were on holiday and it had been raining for days. They were bored stiff until the hotel owner allowed them to go up to the attic to find something to keep them amused. They found an adventure!
An old sea chest and a ghostly apparition sets them on the path to discover Cap'n Billy Bones' treasure. A map of the coast, a rhyme written by Billy Bones telling of the treasure. A midnight visitation from Cap'n Billy's ghost warns of danger.
A cliff path, a smugglers' cave, a trap door, a hidden cellar and a secret tunnel all lead to danger. They're trapped, the sea in front of them, an immovable trap door behind. Will they be rescued, will they survive?