The Secret of the Roman Ruins

The famous five set off for a few days to a wild island. But, as it turns out, they are not alone here. At night, something strange happens on the island. Someone is trying to scare them by peering through the window and staging a fireworks display of ghostly lights. What are these people looking for in the abandoned cottage? Why do they want to make the kids leave as quickly as possible? And how is this pursuit connected to the excavations at the Roman ruins taking place on the island?..